Benjamin J. Heckendorn built a PS2 portable with LCD display - Really an amazing Hack.
When the new Sony PS2 came out some people thought it would be like the PSOne featuring a integrated Display for portable use. Well the PS2 just got slim and features a integrated network adapter.
So Mr. Heckendorn created the PS2p with integrated battery and LCD Screen. The screen comes from a PSOne. Check out the step by step build report.
Not sure if this portable PS2 is cheaper than the new Sony PSP - Pre-order Japanese Sony PSP now for $219.90.