I bought a DSM at your age... but I was also a huge psych geek and knew that was what I was going into as a profession. Looking back, it was a waste of $50 since it keeps changing. There can be some interesting disorders to read about, but it doesn't tell you much other than diagnostic criteria. You don't want to go diagnosing yourself or anyone else
As for good intro books, most intro texts are pretty much the same. Very little has changed in the basic texts over the years, so you can grab any intro text and read away. If you are interested in some more info on psych disorders, look for an abnormal psych text. It can be a bit heady, but interesting. That I would try to find a newer version of though, as a lot changes in what they publish and agree on.
There's a lot of info on the web, but I would recommend sticking to more reputable sites like apa.org, the one for the american counseling association, or national association of social workers, and not wikipedia or anything like that. pc also has a lot of good info (though maybe stay away from the blogs if you are looking for more educational stuff. I find the blogs a lot like the psychology today website and any other forum geared towards attracting readers. There's good basic info on there, but nothing too in-depth).

Is there anything you are particularly interested in? Or just looking to expand your psych knowledge?