Lumines is great, but I'm not that sure it would appeal to an 8 year old kid. It's basicaklly a very simple tetris style block puzzle game, but the little I got to play it yesterday (about 4 hours) it might be too difficult. But I did get better and better at it the more I played, although first I had difficulties finishing the first "skin".
At it's basic it can be a tad too repetitive, but it really is the music + visual style that is a very big part of it's appeal nad as you get better in it you do get more "at one" with the game, and that feels great.. another of those "zone" games.
If your kid is not into that kind of things and puzzle games there might be better alternatives.
Ridge Racer is very good too, and maybe more into your kids tastes. It has a very gentle learning curve, so as while the later stages are very very hard, there's a plenty to play through and fun to be had even if you're not a Ridge veteran.
Haven't really tried any other games, but that Legend (don't remember the whole name, but that PS2 Baldur's Gate type game) sounds like a game kids would like, not too demanding but a fun hack and slash game. A game that should be easy to pick up and play.
A 512 MB card should be good enough to hold three or four half hour tv episodes.
I have the British "Coupling" series that were originally about 700MB/episode avi, and encoded them with PSPVideo9 to about 120-150MB's each.
I could only fit one of them at a time to my 256MB card. The PSP allows you to use only 227MB, and if I tried to put two episodes on it it would've always exceeded the 227MB (nowm 226MB with a couple of game saves) limit by a couple of megabytes.
I didn't use the maximum quality PSPVideo9 setting, but some less. With max they would have been about 230-250MB.
With a fully charged battery I was able to watch 6 to 7 hours of video from Memory Stick.
