I have roughly $400 to spend and need some advice...

For one, most PSP titles are poorly done PS2 ports. Framerate issues, slow loading times due to the UMD format, sloppy controls... All very common problems with PSP games. I also find it uncomfortable to use for more than about a half an hour at a time. The analog thumb stick on the PSP is too close to the edge for larger western hands, it was clearly designed with smaller asian hands in mind. The screen is also bothersome to me. The resolution just seems too high for the size of it, and it's uncomfortable to look at. There also seems to be a real problem with dead or stuck pixels on PSP screens, which aren't usually covered by any warranty, unless they exceed some number.

You can get a Wii pretty easily on eBay if you're willing to take the risk. Right now, there's a lot of opportunistic people buying them up, then turning around to sell them on ebay to make a quick buck. Of course, the Wii is still pretty new, and is a bit of a departure from console norms, so games are still a bit scarce and I suspect most of the first round of games will be pretty awful. They'll be rushed out the door to try and cash in on the Wii's popularity. It's also going to take some time for game developers to wrap their heads around the Wii's control system. With the Nintendo DS, you tend to have some games that are really well done, make use of the dual screens and stylus very well. You also have games that don't really "get it", and are not the most pleasant experience. You still have the GameCube backwards compatibility with the Wii if there were any games for that console you were interested in, but it'll probably be a good year or so before Wii games stop sucking (aside from Twilight Princess).

Not being too far removed from my college days, I'd say save your money. College is expensive, and you never know when $400 will come in handy. That was about the average cost of my books for a semester my first couple of years. But think about it... Your car may break down, some of your stuff could easily be stolen or broken if living in the dorms, you may need bail money after getting busted for underage possession of alcohol at some kegger... College is a never ending source of ways to bleed you dry financially.

There's also a very good chance that you won't have much time for playing games anyway. At least where I went to school, group projects seem to be all the rage. Along with every professor being an arrogant ***** and assuming that theirs is the only class you're taking, or should care about, and piling on the homework like there's no tomorrow. IMO, this is far more likely the cause of all these school shootings than violent video games and TV. People snap under the stress, and go nuts. And after your first really bad group meeting, you'll probably be entertaining a few fantasies of mass murdering your fellow group members. The important thing to remember though, is not to act on them, or even dwell on them.

Anyway, I would save your money, at least for the first semester. Then, once you've had some time to adjust to college life, and the reality of college life has been separated from your fantasy, you can decide what you want to do.