I'm going to response solely to the question "What would probably be most useful in college?"
I'm in college. I have an MP3 player, and love it. I have an XBox, and I don't play it that often. I have a Palm Tungsten E and I love it. I don't have a camera, yet.
At My College:
Everyone but me has an iPod. You won't really impress anyone with an iPod, or an iPod photo, for that matter. As a matter of fact, you stand out more if you DON'T have some kind of portable music player.
Some kind of organizer can be very, very, very, VERY helpful. My life is on my Palm. At the same time, you don't need it to do a lot of fancy stuff. If it can keep track of your classes, work, homework, etc it is sufficient. I will admit that people with the coolest PDAs look more important and intellectual, as sad as it is!
As far as the Playstation goes, I don't think a PSP would be where you should spend your money, especially if you have some normal way of entertaining yourself, like a non-portable game console, or a gaming computer. You don't need a Playstation in class. Don't get a PSP.
About the camera. I recommend getting one you like. After one year of college, there are a million things I wish I would have memories of, that I don't. That's why I'm in this forum right now. I'm buying a camera. At the same time though, it doesn't have to be a great camera.
I recommend having some variation of all of these (the list you gave). If you have some and not the others, spend the money to get a cool whichever-one-you-don't-have. You'll be happier having 3 mediocre gadgets and one really good one versus replacing one you have with a really good one, and missing another. Does this make sense?
I've been thinking about certain gadgets as a reward for graduating from high school. Here are the products I had in mind:
1) the Apple iPod Photo(30gb)
2) the Treo 650
3) the Sony PSP
4) a very slim Casio digital camera (upwards of 5 megapixels)
Here's the thing: I find the iPod useful because I can transfer my photos from my digital camera, and so I virtually have unlimited space. However, I only have about 5 GB of music, and I don't even listen to them all - just my favorites. Therefore, the storage space on the iPod might seem unpractical.
I like the Treo 650 as a convergence product. I was 13 when I first bought the Palm m100 and have used it ever since. The Treo would combine the features of the m100 (and more, of course) and my cell phone, and I would have less to carry around. I use my m100 regularly, since I upload things like study guides for tests on it. I also like the fact that I can use the Treo 650 as an mp3 player, but with the average battery lifetime of 4 hours, I'm left hanging in the wind.
Nearly the same story with the PSP. I like how it can be an mp3 player, but I'll have to pay extra for the memory sticks (like at the 1 gb capacity). I'm reluctant because I don't often play games on the road; I just watch movies on my laptop instead.
Now with the digital camera, I'm dragging around a FujiFilm FinePix S5000. It's just so...big.
So what should I do? I feel like if I wait long enough, one such company will combine the features of the iPod photo and the Treo 650, and possibly a digital camera (example? the mrobe 500 by Olympus). Would it be wise to invest in a nice basic mp3 player (such as the recently released Samsung YEPP player) and stick to my m100 and my cell phone?
Help me out here! I'm dying for my own little gadget to show off! What would probably be most useful in college?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic