no love for the msp?
http://www.ti.com/lsds/ti/microcontroller/16-bit_msp430/overview.page?DCMP=MCU_other&HQS=msp430 pros:
cheap: less than $5 to get started with a development board and two chips - and lots of free sample chips available if you ask nicely and don't abuse the service.
cons:
mind manglingly confusing code and what seem like epic war and peace datasheets for beginners.
not so much online support, although this is slowly changing.
you can kinda port arduino code over with a little homework and energia:
http://energia.github.com/Energia/ depending on chip and function.
conclusion: cheap but hard work. worth the effort depending on the intended project and how much you value your time.
http://omfootctrl.sourceforge.net/if you just want something that works in a hurry i would just hack a usb keyboard - google will help you out in this regard.
for an easy intro into c i found these video's quite entertaining:
http://www.youtube.com/playlist?list=PLD61C018D7DC1F431*edit* when i say cheap: avr = £4, pic = £2 and msp430 = £0.50 for individual ic's. averaged prices, but still... depends on your purpose - do i want to flash a few led's in sequence or do i want to sample, store and recall data? you wouldn't put a quad op amp in your project if you only needed a single buffer, would you?
digital control: analogue sound
would you rather mess with a bunch resistors on breadboad for half a day or would you rather do the same math via usb on a gui in half the time? i know what your boss would prefer you to do with your time - i actually enjoy both but this is just a hobby for me. horses for courses, choose your poison, etc. fun, fun, fun.