Make Pt1018
Pandora, the open, highly hackable console is available for pre-order, looks pretty nice. Not open source hardware, but not too shabby! More @ wikipedia and their site

The Pandora system will have an open source, Linux-based OS. The Pandora is designed to be a handheld game console, with PDA capabilities.

One of the main uses of the Pandora is for homebrew gaming and the emulation of older computer systems and video game consoles, which is possible through efficient use of the resources made available by the Texas Instruments OMAP 3530 SoC. The Pandora developers have already shown working emulators for PlayStation, Amiga, and Sega Mega Drive software,[3] and the Pandora is thought by its developers to have the potential to emulate most if not all machines older than the PlayStation (notably including the Super NES, the Nintendo Entertainment System, and the Atari Jaguar). The Pandora’s keyboard and touchscreen should allow interaction with Commodore 64, ZX Spectrum, MSX, Atari ST and other classic home computer emulators.

In addition, the powerful processor and GPU may provide the potential for development of emulators of more advanced systems such as the Nintendo 64.

The Pandora uses standard libraries such as OpenGL ES and SDL freely available, allowing anyone who wishes the ability to develop for the system. Many developers from the GP2x community have publicly stated that they will be developing applications for the new system.

The Pandora will have an existing software base due to having a package manager that will accept Debian packages for the ARMEL (little-endian ARM) architecture.