I just finished this up a few days ago. This is my first portable, so I wanted to keep it simple. I did this project not for the end result, but to test my abilities. I know what you're going to say, it needs a bigger screen. I partially agree, but I wanted to keep costs low for my first one. It has a 3.5" ebay screen as well as a 2000 mAh battery. I am amazed with the battery life I have gotten so far. I have not run it dead yet, and I estimate that it will last well over 2 hours (I charged it for an hour or two last night, and I have played it for over an hour and a half today (and it takes 5 hours to fully charge)). There aren't any speakers, but there is a headphone jack. The original multi-A/V jack was preserved, in fact this is compatible with every n64 accessory except the original power cord. One advantage to this simple design is that it could be reproduced fairly cheaply.
I brought it to school today and amazed everybody. I think I might have even sold it. If this one is sold I will probably make another using the same design (only probably a 7" screen for multiplayer). I'll post a full build log, probably in the form of a tutorial, when I do make a second one. Overall, the experience was a great way to get started in the world of portabilizing.
I have a few questions for anyone who reads this: What would you pay for something like this? What would you name it

?
Thanks for reading!
More pics here:
http://s905.photobucket.com/albums/ac25 ... ble%20N64/" onclick="window.open(this.href);return false;
Edit: Just thought I'd mention that the n64 case is no more beat up then when I started, lol. I still have a bit of cosmetic work to do.