I just wrapped up a new blog on how to create your own retro handheld on the cheap if you don't have any skills with soldering or don't have a 3D printer available or simply don't feel like doing the work to build your own or to find an open source unit.

http://retrogamingroundup.com/blog/?p=1307

The basic idea is to take a budget android smartphone (I use the Blu R1 HD for its rock bottom pricing and decent specs) with a solid 8BitDo NES30 Pro controller and their Xtander mount to create the handheld. Using free software such as Retroarch for all the emulators and Gamesome as a frontend (also can be set to lauch when Android boots) creates a budget handheld for around 110 bucks. Check the blog link for details, pics, and videos.