If you're not in med school yet, I'd definitely consider looking at a 2nd job that doesn't take up too much time. I know this sounds stupid, but selling things (not your own, buying and selling inventory) on ebay can actually be fairly decent money. No, not those cheesy late night TV ads, but real ebaying.
I remember when I was in high school I'd look on ebay for prices of stuff I'd see at closeouts and stuff (there was actually a closeout store right by my school back then, they've since gone bankrupt [ah, irony]), and sell a few things for spending money. Now, the stuff I sold back then would hardly make me any money today just because ebay fees have gone up so much, but still, there's plenty of money to be made if you can get a good deal on stuff.
If it was earlier you could have actually bought toys at wholesale from the toy manufacturers (popular toys anyways) and sold them for quite a decent amount of money, but it's way too late for that now since it's already december and it takes forever for them to ship to you (plus they're already sold out of anything profitable by now). I know a lot of fairly big-time ebayers, and several of the ones I know make in the 6 figures. They're not *just* ebayers though, since ebay isn't good for selling some sorts of things, so they sell elsewhere too (own internet stores, Amazon, classified ads in the newspaper, etc.)
It's not really very glamorous, but if you're lucky and willing to put some money on the line every now and then it's decent returns.
Earlier this year I got VERY VERY lucky, because the Apple store was clearancing Sony HDV-FX1 camcorders (a very high end HDTV camcorder) for $2000. Which sounds expensive but it's a $3000 camcorder. Anyways I ended up selling them for like $2800 each on ebay, after managing to score 3 of them.
That made up like, half my entire year's ebay sales profit
(I obviously don't ebay very high volume-I have to work full time and I was studying for the MCATs so I basically didn't sell anything this year).
Anyways, it's fairly hard to get that lucky but, if you keep and eye out for such things you're almost sure to be able to make a little bit of money.
Oh if you're clever you can look on ebay to see what people are selling and try to figure out where they're buying it. I remember doing this back in the old old days.
If you want to get off to a decent start on buying random cheap stuff just start looking at those bargain hunting websites, like Fatwallet, etc. People will post bargains they've found and such, although usually there's nothing particularly profitable, but even on popular websites there will occasionally be something pretty good. Of course, anything popular will mean that about 10,000 other people will have already purchased the item and tried to sell it on ebay, lol. Still, if you have no idea where to start, that's a start.
Optimally you'd find things to buy and sell yourself, and start figuring out if there are actually decent things to buy wholesale, etc. Of course I'd only do that if you seriously wanted to do it, if not I'd just stick to selling the occasional thing you found cheap.
Also, if you have a lot of junk sitting around, you can start by selling all that junk you don't use for some money to tide you over for now. Plus it'll build up your reputation on ebay anyway.
to you. 
