Screencapping programs?

I've been thinking about downloading a screencapping program so I can make my own screencaps, but I don't even know where to start, LOL. Someone on my flist recommended VLC player and I know there's at least a dozen more programs out there. So which to choose? I looked at PowerDVD, but I'm not interested in purchasing anything, and it looks like you can only get that one as a free trial. Any suggestions on which program is better than the other? Thanks in advance. :D