http://evilmadscience.com/productsmenu/tinykitlist/310-diavostart
 
Hey all, if you need some more ‘duinos in your collection check out this deal, but hurry it ends today-night?
 
Kit Includes:
5 Diavolinos (think Arduino Decemilanove / Uno equivalent with USB interface, AVR  socket, & voltage regulator left off) – these are kit form, you must assemble.
1 USB-FTDI interface (for programming). USB cable included
2 5-volt 1A (regulated) wall warts – to power 2 Diavolinos (includes 2 jacks for Diavolino PCBA)
3  3xAAA battery packs – to power the other 3 Diavolinos
Crystals, caps, resistors, headers, switches needed to assemble 5 complete Diavolinos.
 
While these kits don’t include the voltage regulators there is a place on the PCBA for you to add your own.
 
$68 + $5.15 shipping for a grand total of $73.15.
So, break that down to five Diavolinos @ $14 each + $3.15 for 2 wall warts & 3 battery packs, delivered to my front porch.
Not bad, not bad at all…

Maybe you want to check out tinyUSBboard.
It may not be the prettiest board, but it has an onboard USB-Interface and does not need any serial programmer. (Not even for updateing.)
Maybe is the cheapest and easiest arduino compatible board of its class, too?

Website: http://matrixstorm.com/avr/tinyusbboard/

Have fun!