In my early days of Wikipedia, I did a lot of vandalism reversion through special:recentchanges. I've come to do a lot less of that nowadays. I don't really focus on any one area, instead doing a hodgepodge of tasks. I focus a lot on academia (from universities to standardized tests), as well as doing some work in politics (although I've found that — not at all surprisingly — these are hotbeds of POV, bad faith, and even sockpuppetry). I still do a lot of vandalism reversion through my watchlist, but I also add in bits and pieces of information to articles, whenever I find a good source. Resources like Flickr and federal government websites have given me great tools to find acceptably licensed material to illustrate articles. I also do a lot of small tasks here and there, like fixing typos, finding geographic coördinates, and improving citations. I'm generally happy to help out if I can, so if you see something that needs doing, don't hesitate to drop me a line
Library and school databases. Wikipedia can only grow so far as its references. Lots of newspapers and magazines are unavailable through normal methods, especially editions older than 7 days. These databases contain largely untapped treasure troves of knowledge. Their search functions are usually pretty good, and you don't have to have a specific article in mind, you can just jump in and see what you find. You also don't have to separately jump from one newspaper's website to the next: it's all in one spot. You're school and public library probably provides you free access to these with your library number, so go to your local/school library and add a (properly cited) reference or two.
Wikipedia:Media copyright questions. Raul has some laws about Wikipedia, one of which states, "For every one person who knows something about copyright law, there are at least ten who don't, and two who think they do but don't." I am not the first (but I'm learning!), and rather than attempt to be the third, I defer to those more knowledgeable on the subject than I. If you are someone who knows about copyright, your services are greatly needed. If you aren't, then better to ask before you make a mistake rather than after.
User:SuggestBot. Don't go looking for articles that need help, let this bot find the ones you will enjoy working on.