I've used a bunch of different mikes. When recording on a computer (with no external mixer), I generally use a Sony digital recording mic. I can't remember the model # right now, but it has the 3.5mm plug on the end, so it's already ready to go into the computer. This is usually what I'll do for my personal recording projects.
At school, however, I have a full studio to play with, so my options are a bit better. There, I'll generally use a Shure SM58 for vocals, and I'll play around with different stuff for instrumental. I'm not really allowed the top end, since I'm not actually a recording student.
For recommendations - If you're looking on the mid- higher end, I've always liked the SM series for Shure. The SM57 has better shock mounting, but the pop filter isn't as great (you'll just need a new pop filter). It is uni-directional, though, which can be very nice if you're in a noisy or busy environment (computer, florescent light, furnace, fridge, etc). The SM58 is a bit warmer and has a better pop filter, but I've broken a few of these because of bad shockmounting. they're also multi-directional, which can cause background noise problems, but it does increase the depth of whatever is being recorded.
On the mid-end, Behringer makes a nice line of multi-purpose mics for $29-$69. Anything unidirectional with a wide base, shock mounting, and a decent pop filter will work well for vocals. If you want the full depth of your voice, get a multi-directional mic and just find a way to silence your environment. Sony also makes a great line of digital recording mics with PCs and Minidisc recorders in mind, but most of these mics require the device to supply power through the audio jack. As far as I know, this can only be done with certain Minidisc recorders. If you're laying vocals on existing tracks, this really isn't an option, but it's actually a nice way to record acoustic music, as well as live performances.
