Greetings fellow Tenno!
This guide will simply show you where you will find the material needed for all the crafting in the game!
Loot/Material will be shown as the image when dropped.

There's also as of update 8 (I think) there was a new kind of resources that could be dropped on certan missions. These included materials that would only be used in the research and crafting of weapons in the Clan-dojo which can be accessed by a Clan key that you can craft by clicking the little button to the right of the "Play now" button.
These will look like the normal material when dropped aside from the fact that they are blue instead of orange. (Compare pictures)

There are three different categories that you can devide the materials in, Common, Uncommon and Rare.Common will be the ones you will most often find, next on the list is Uncommon and last Rare. *Explenation down this section*

Let's start with the common ones.

• Ferrite: Mercury, Earth and Neptune.
  
• Circuits: Ceres, Jupiter, Europa and Venus.
  
• Nano Spores: Eris, Saturn, Neptune.
  
• Polymer Bundle: Uranus, Mercury and Venus.
  
• Salvage: Mars, Jupiter and Sedna.

Uncommon.

• Alloy Plate: Venus, Ceres and Sedna
  
• Plastids: Saturn, Uranus, Pluto and Eris
  
• Rubedo: Earth, Europa, Sedna and Pluto ( Extremely high drop rate on Europa Robert Puttinson 2013-05-05 )
  
• Oxium: No specific planet but rather from a specific enemy. The Oxium Osprey. Find them on Corpus controlled nodes. *Note: These drop in about the same quantities as rare resources, but are much more common*

Rare.

• Control Module: Neptune, Void
  
• Gallium: Mars, Uranus
  
• Morphics: Mercury, Mars, Europa, Pluto
  
• Neural Sensors: Jupiter
  
• Neurodes: Earth, Eris
  
• Orokin Cell: Ceres, Saturn, Void *Note: ALL bosses have a chance to drop Orokin Cells, but those on Ceres and Saturn have an increased chance due to it being a resource 'native' to those planets*
  
• Argon Crystals: Found in the Void *Note: These decay for every day they are out of the void. If you're going to use them to build something, gather some quickly*

Common Resources.
Common resources can be found in quantities of hundreds at a time. They drop from lockers, breakables, normal enemies, and bosses. These usually drop in quanties of +50

Uncommon Resources
Uncommon resources can be found in quantities usually between 10 and 50. They drop from lockers, breakables, normal enemies, and bosses.

Rare Resources
Rare resources will usually drop in quantities of 1-3. They are most often found by defeating bosses, and very rarely from normal enemies or storage lockers/containers. All rare resources can also be found from assassination targets, such as Councilor Vay Hek and General Sargas Ruk.

These will be used to build the different weapons from the Clan-dojo.
These resourses will include the following.

• Detonite Ampule
  
• Feildron Sample
  
• Mutagen Sample

They will be dropped on the following planets.

• Detonite Sample: Mercury, Earth, Ceres, Saturn, Uranus, Sedna.
  
• Fieldron Sample: Venus, Mars, Europa, Neptune, Jupiter
  
• Mutagen Sample: Orokin Direlects, Eris

Special items are the items not used for crafting weapons or warframes, but rather Keys.

Nav Coordinates

• Nav Coordinates can be found in any mission, however, you must break crates. Try and find a mission with lots of crates or containers.
  
• Golem Nav Coordinates can be found by looting containers in an Orokin Direlect type mission. You'll need 5 Nav Coordinates to get to 1 mission with Golem Nav Coordinates.

Beacons

• Omega Beacons are the most common type of beacons. They can be found on Ceres, and are obtained by killing Prosecutors.
  
• Kappa Beacons are the second most common type of beacons. They can be found on Ceres, and are obtained by killing Prosecutors.
  
• Gamma Beacons are the uncommon type of beacons. They can be found on Ceres, and are obtained by killing Prosecutors.
  
• Delta Beacons are the rarest type of beacons. They can be found on Ceres, and are obtained by killing Prosecutors.

Pictures will be added shortly.

Locations:
This list will contain my own experiences aswell as the opinions from other players so this might not be the correct places to farm on.

• Alloy Plate: Kiliken (Venus) or Venera (Venus)
  
• Control Module: Hyena (Psamathe, Neptune) or Raptor (Naamah, Europa)
  
• Circuits: Varro (Ceres)
  
• Ferrite: M Prime on Mercury
  
• Morphics: Sgt. Nef Anyo (War, Mars) or Captain Vor (Tolstoj, Mercury)
  
• Neural Sensors: J3-Golem (Themisto, Jupiter)
  
• Neurodes: Councilor Vay Hek (Everest, Earth)
  
• Rubedo: Valefor (Europa)
  
• Salvage: Io (Jupiter)
  
• Plastids: Ariel (Uranus)
  
• Polymer Bundle: Desdemona (Uranus)

Tips:

• If you are not doing a speedrun on a mission the following should be done everytime, BREAK EVERYTHING! oh, and loot lockers aswell. This is pretty self explanitory, but try to look for the unlocked containers/lockers and the breakable crates during your missions.
  
• Explore the whole map! Even the parts which are not related to the current objective. This is not super popular to do on a multiplayer mission with people who are impatient and will set off the timer for the compleation of the mission.
  
• Defense missions with infected will spawn a ton of enemies that will increase your chance of getting drops. *Note: This usually only happens during infestation outbreaks or during an Orokin Direlect Defense (ODD)*