My reference for multicopter drone projects is the multicopter wiki comparison table. I dug into two:

They are most based on the same hardware parts, i.e. Arduino platform for the processing unit, Sparkfun IMU and sensor boards and Hobbyking for the engines, ESC, ...

Part List

Here is a rough list for hardware and the associated price (French shops preferred). Part list for AeroQuad can be found in the tutorial. Part list for Shrediquette can be found in Shrediquette - FAQ's.

Control Board

IMU

Engines

ESC

Propellers

Servo

(Only for trirotors)

Frame

The frame itself is quite cheap to build. Just a square aluminum tube and thin plywood will do (according to Schrediquette!)

I should have a deeper look at all those parts to figure out which one I really need, and which one I should go for. For instance motors should be chosen according to my drone's weight. ESC should be chosen according to motors, same for propellers. On the electronic side, I must have a look at all the listed IMU to see the differences. Schrediquette uses very expensive gyros which might be replaced by a combo board. The control board should be chosen according to the IMU output: analog means enough ADCs on the read the sensors, ...

Done for today, I'll keep you posted. A+