The new firmware version of Curious Inventor’s MIDIATOR Kit lets you map any button or joystick on a game controller to any MIDI note or controller, including button pressures.
For instance, you could make the vertical axis of the left joystick go from 89 at the bottom to 34 at the spring-returned center, to 5 at [...]

Things to Come Records posted some nice Flickr shots of the Voice of Saturn Sequencer & Synthesizer. 
These are a couple of cool synth DIY kits that should be suitable for even beginners. 
 

DIY kit maker CuriousInventor has introduced a new music sequencer kit, called the Voice of Saturn, that looks like an inexpensive way to get into analog sequencing.
This is a 10 step analog sequencer, which basically steps through 10 different [...]