Simple breakout board using the dirt cheap IC’s CH340G ($0.30/each on ebay) for Serial and a AMS1117-3.3 ($0.025/each) for power. Breaks out all pins from 2mm to 2.54mm headers. Plugs nicely into two small breadboards for prototyping.

Ordered and tested. Works like a charm: http://jcprojects.tumblr.com/post/155454738769/my-omega2-onion-shield-using-a-ams1117-for-33v With Ebay components and OSH park PCB’s, these should cost maybe $6.50 in parts.

BOM:
1   LM1117  Fixed 3.3V/1A Low Dropout regulator
2   18pf    Unpolarized capacitor    (C1/C2)
1   100uf   Electrolytic capacitor  (C3)
1   10uf    Unpolarized capacitor   (C5)
1   0.1uf   Unpolarized capacitor   (C6)
1   CH340G  Serial interface    
2   16 pin header (2.54mm)  
2   16 pin header (2.00mm)  
1   12Mhz   Two pin crystal 
1   USB_OTG micro/mini connector