Noob Synth

[velbright]

Do you have any recommendations for a simple cheap synth that a noob like me can build?

[synthgeek]

Atari Punk Console

or


Weird Sound Generator

or maybe

one of these

[angry_droid]

An SX-150 is easy enough that a cat could build it.
And there's mods aplenty for it after you get bored with it. 

[ralphw]

There are some Arduino/ATMega-based Synths, as well as MIDI and CV (control voltage) "shields" to allow for more experimentation.

"Audino"- an code and other Arduino projects at http://code.google.com/p/tinkerit/

http://www.arduino.cc/playground/Main/SID-emulator (if you like the SID chip)

http://www.avishowtech.com/mbhp/mbhp_core32r1.html (if you like the ARM chip)

SN Voice is another interesting project, although some of the components besides the SN76477 are hard to find.  There are forums on multiple sites, search Google for SN Voice