Where can I get prototypes assembled?

[Opendous Support]

I know of a project that used MyroPCB to have 3 prototypes
assembled. Expect costs of around $100/board.
http://treadgaming.blogspot.com/2011/03/myro-pcb-fabrication-and-assembly.html
http://treadgaming.blogspot.com/2011/04/treadgaming-pcb-v10-is-here.html

I have worked with GoldPhoenixPCB to have larger lots assembled.

I DIY prototypes to save money and not have to wait month(s). There
are many tutorials for DIY reflow (at Instructables.com, for example).
Start with a simple project to figure out the technique and move up
to complex/expensive projects.
http://code.google.com/p/micropendousx/wiki/MicropendousX_LPC183x_Prototyping

Reflow one board at a time and know that you will fry your first
several reflowed boards so attempt a cheap and simple design.
http://code.google.com/p/micropendous/wiki/Micropendous_32U2

For a board such as the above with its wide-pitch parts you can
simply spread solder paste with a syringe dispenser on all the pads
and it will reflow correctly. You may need to remove the odd pin
short with some flux and solder wick.
http://www.seattlerobotics.org/encoder/200006/oven_art.htm
http://search.digikey.com/us/en/products/SMD291SNL/SMD291SNL-ND
http://search.digikey.com/us/en/products/425/473-1062-ND
http://search.digikey.com/us/en/products/SMD291NL/SMD291NL-ND

For finer pitch parts you will need a stencil (OHARARP or Pololu).
It should not be an problem to find someone who will split a stencil
order with you.
http://ohararp.com/Stencils.html