Also work in this (general) area... my thoughts...
A few general things before you get down allocation:
In a market downturn, don't pull your money out to "wait for things to get better." It'll work against you. If you have real problems doing this, stop opening your monthly statements. Seriously.
Try to set up a minimum amount to contribute monthly and stick to it. Like others said, if your employer has a matching program, do as much as you can to take advantage of that.
If you have any longstanding credit card debt or other high interest debt, pay that off before you start investing anything.
Vanguard is a superb choice - at your age you could just buy into their product that mirrors the S&P 500 index and keep adding your monthly contributions to it and that'd be a pretty good route. Well down the road, you might want to start putting your contributions into bonds etc, but that's years away. Of course if you start feeling very flush you can start getting into "aggressive" funds. You'll find, however, that without dedicating a significant amount of time, these are hard to pick well, and there's not a lot of evidence you're going to be missing out on much or ANY extra performance by being in the overall market instead.
If you want to spend a lot of your freetime in the future studying funds, individual stocks, etc, that's AWESOME and might lead to higher returns. I'd tell anyone to spend serious time (over a year) studying up before trying to pick stocks or funds focused on any particular sector, and even then keep the amounts small to start.
It's an awesome move to get on top of this, by the way. Feel free to toss up any other issues that arise.