I'm not aware of such a useful tool... sounds like a fun challenge though!

Don't make a suggestion you don't want to work on :)

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There probably is, but let's see if I can tell you what you want to know.
It turns out almost everything that can be considered a resource can be exchanged for something else, and usually can be exchanged for either another resource or something that can be broken down into resources, so here's a rundown of everything in the Inventory screen that I can get a look at.

Planetary materials:

• These are used to upgrade weapons and armor of every type
  
• Spinmetal leaves: found on Earth, indoors and outdoors
  
• Helium coils: found on the Moon, mostly on the lunar surface, rarely inside human structures and basically never in Hive structures
  
• Spirit bloom shavings: found on Venus, often next to plants, rarely inside structures
  
• Relic iron shards: found on Mars, indoors and outdoors
  
• The Crucible Quartermaster and Vanguard Quartermaster exchange Crucible and Vanguard marks for all of these (10 marks for 20 materials)
  
• All of these can also be found in chests, which spawn in caves, on ledges, and in other out-of-the-way places
  
• Getting your Grimoire score for a destination high enough increases how much of a material you can get from one node (e.g. one set of helium coils) in that place
  
• Can also be earned by completing the daily heroic story mission or certain bounties

Ascendant materials:

• Ascendant shards are used to upgrade legendary armor from before House of Wolves, including raid gear
  
• Ascendant energy fills the same role as shards but for (older) legendary weapons
  
• Can be found in chests the Vault of Glass (and Crota's End?), and by completing public events (immediately and in reward packages), and rarely in the Crucible and in chests
  
• Dismantling older legendary gear (including class items) produces shards or energy
  
• New legendaries don't make use of these
  
• The Speaker exchanges energy for shards and shards for energy (for a fee of 50 glimmer), and also exchanges shards for motes of light (2 for 1 mote), glimmer (1 for 250 glimmer), and other things depending on what DLC you have

Radiant materials:

• Introduced with The Dark Below
  
• Used for some legendary armor and weapons introduced with TDB
  
• Earned in some (all?) TDB story activities
  
• Radiant shards fill the same role as ascendant shards for applicable armor
  
• Radiant energy fills the same role as ascendant energy for applicable weapons
  
• Eris Morn and the Speaker exchange shards for energy and vice versa
  
• New legendaries don't make use of these

Runed cores and embalming orbs:

• Used to upgrade some TDB gear
  
• Can be bought from Eris (and I believe earned from TDB activities)

Armor cores and weapon cores:

• Found in the Prison of Elders
  
• Given to Variks the Loyal in exchange for legendary gear

Tokens of Judgment, Flight, and Identity:

• Given to Variks for class items, ships, and shaders, respectively
  
• Can be dismantled to gain a little House of Judgement reputation (10) with Variks
  
• Found in ether chests and the Prison of Elders

Treasure keys:

• Used to gain access to House of Wolves loot
  
• Can be found in ether chests and in the Prison of Elders
  
• Given as a reward for your first completed Wolf bounty each week

Passage coins:

• Used to buy things from Brother Vance to help you with the Trials of Osiris
  
• Can be earned from completing many types of activities and found in ether chests

Etheric light:

• Introduced with House of Wolves
  
• Used to "ascend" legendary gear
  
• Can be found in the Iron Banner, the Trials of Osiris, the Prison of Elders, and rarely through other means
  
• Ascending increases maximum attack to 365 for weapons and increases maximum defense, light, and other stats for armor
  
• Older legendaries still need to have their attack and defense nodes unlocked and activated to be fully upgraded
  
• Some new legendaries come "pre-ascended"

Exotic shards:

• Introduced in late fall of 2014
  
• Used in the last upgrade node of exotic gear
  
• Used to ascend all exotics
  
• Are sold by Xur every week for 7 strange coins
  
• Can be obtained by dismantling any exotic gear

Glimmer:

• Generic currency and upgrade material
  
• Can be earned in every activity and gained by breaking down any weapons or armor
  
• Doesn't take up a material slot and is shared between all characters

Motes of light:

• Obtained by earning XP after level 20, opening chests, and completing many types of activities
  
• Used to pay for reforging new legendary weapons with the Gunsmith, buy exotic engrams from Xur, or buy class items and emblems from the Speaker
  
• Dismantling new legendaries produces motes of light rather than shards or energy
  
• Xur exchanges strange coins for motes (1 for 1)
  
• The Speaker exchanges ascendant shards for motes (2 for 1)

Strange coins:

• Used to buy things from Xur
  
• Can be found in chests and earned from completing (almost?) any activity

Mission items:

• Received for completing story missions and occasionally for other things
  
• Turned in to the person indicated for rewards

Bounties:

• Received from bounty trackers, Eris Morn, Petra Venj, and Lord Saladin
  
• Turned in to whoever issued them for glimmer, reputation, and occasionally other rewards

Marks:

• Used to buy legendary gear from Tower vendors
  
• Vanguard marks are earned for completing basically everything that isn't a Crucible match, a raid, or a strike or story mission done on a low level
  
• Crucible marks are earned for completing any Crucible match-- 2 for a loss, 3 for a win-- and are used with Lord Shaxx, the Crucible Quartermaster, and each of the factions

Commendations:

• Introduced just before The Dark Below
  
• Came in different flavors for the Vanguard, Crucible, and each faction
  
• Were earned by ranking up and used to buy most of the gear from whoever they went with (Crucible, FWC, etc.)
  
• Discontinued with House of Wolves-- cannot be earned now
  
• Can now be used to gain some reputation with whichever group they belong to or as a hipster status symbol

Armor parts:

• Used to upgrade armor of blue tier ("Rare") and above
  
• Can only be obtained by dismantling armor (including class items) of green tier ("Uncommon") or higher
  
• Are class-specific
  
• Sapphire wire: used in Hunter armor
  
• Hadronic essence: used in Warlock armor
  
• Plasteel plating: used in Titan armor

Weapon parts:

• Used to upgrade every weapon of blue tier ("Rare") and up
  
• Used as payment for reforging newer legendary weapons
  
• Can only be obtained by dismantling weapons of green tier ("Uncommon") or higher (despite the hover text for blue-grade weapons still saying you can get them from the Gunsmith)

Ammo synths:

• Fill you to capacity on whichever type of ammo is in the name (primary, special, or heavy)
  
• Can be found in chests and bought from various vendors, and are given as rewards occasionally
  
• Special ammo synths are sometimes used as payment

Telemetries:

• Speed up unlocking upgrade nodes on whatever type of weapon is in the name
  
• Sold by the Gunsmith and sometimes by Xur, and can occasionally be found elsewhere

Glimmer drop increasers:

• These make low-level AI enemies drop glimmer and high-level AI enemies drop more glimmer, and in some cases are used as payment
  
• They can be found in chests and by killing high-level enemies
  
• Resupply codes: used with Cabal enemies
  
• Blue polyphages: used with Vex enemies
  
• Black wax idols: used with Hive enemies; also used as payment to Eris
  
• Ether seeds: used with Fallen enemies; also used as payment to Variks

Relics:

• Given to a Cryptarch for 200 glimmer each
  
• Can be found by killing enemies and in chests
  
• House banners: Fallen
  
• Silken codices: Hive
  
• Axiomatic beads: Vex
  
• Network keys: Cabal

Jackolytes:

• Introduced in late October 2014
  
• Initially given to each player, now drop from Hive enemies, but very rarely
  
• Unlock a special Sparrow sold by Xur and an item that changes the visual when you die and respawn
  
• Change your helmet/head to a jack-o'-lantern
  
• Overlay your screen with a spooky visual effect
  
• Overlay your game audio with the wails of the damned

As far as getting a good deal, the only overlap in exchanges I'm aware of is Eris and the Speaker both dealing in radiant materials, and I'm told the Speaker gives the better deal. The things you'll want to save up the most are probably ascendant materials, since they can be exchanged for many things but nothing can be exchanged for them and you can't just buy and shard vendor gear for them any more. I would not recommend trading anything for motes of light because they flow pretty freely now and two shards (via the Speaker) or a strange coin (via Xur) for one mote of light does not seem worth it to me. I would recommend against buying ammo synths from Xur for the same reason, but the telemetries-- 5 for 1 coin, unless I'm remembering wrong-- are an OK deal.