Want to build it yourself?
The BitBuilt Forums house the most comprehensive collection of guides, worklogs, and resources on how to build your own portable. This is the best place to learn the information needed to build your own portables. The guide hub section is the best place to start.
The G-Boy Guide
While the G-Boy has been discontinued, a guide on assembly still remains. It’s a great read that shows the process of building a portable, even though the kit is no longer available for purchase.
The G-Wii
Another easier build for beginners to the hobby. While there is not a clear cut guide to this build like the G-Boy, this portable is still a good starting point and is a better choice if a landscape design interests you more.
PS2 Portables
PS2 portables are more difficult than Wii portables, though not to an extreme degree. If the PS2 holds a lot more interest for you than the Wii/GameCube, then the best place to start is the Definitive PS2 Trimming Guide.