I've noticed the same questions tend to crop up again and again. One of the common ones is "Where can I download free music?" These questions generally get a flood of twits recommending Limewire, and one in ten of those actually bother to mention that a lot of the music on Limewire isn't exactly legal.
Below is the response I've taken to posting. I got tired to retyping it again and again, so I'm presenting it here so I can just copy and paste it in the future. If people are going to ask the same question that's already been asked and answered over and over, they might as well get the same answer as everyone else who asked the question.
There are several options for free, safe, legal music and video downloads. A lot of people recommend Limewire, Bittorrent, Bearshare and the like, but most the content on such networks constitute a copyright violation or can be infested with viruses. Most of these programs are also known to have trouble with Firewalls and a few won't run under Windows Vista.
The first legal source is Podcasts. My favorite is Crap from the Past at crapfromthepast.com. The host Ron "Boogymoster" Gerber, describes it as a graduate level course in pop music, and he's not far off. You'll hear a lot of music that hasn't been on the air for a long time. The program is available as a podcast, with three half hour segments coming out a week.
Another great source of Public Domain and Creative Commons music is archive.org. For example, It's amazing how much old school Jazz has fallen into the Public Domain. A lot of techno and pop artists use a Creative Commons license that makes non-commercial distribution legal.
Jamendo.com is a record label that makes all their music available for download for free. The idea is to give away MP3s to encourage people to buy the actual CDs.
Archive.org has a page that lists other labels like Jamendo that offer free, legal downloads of their music.
You can also look into various music Podcasts. For example, there are some really good Celtic music podcasts, Celtic Music News being my favorite. celticmusicnews.com
The BBC and NPR have a variety of music programs, most of which are free downloads or can be listened to as streaming media.
If you use iTunes, the iTunes store has a selection of free music and videos, with new free music being released on Tuesdays. You can even sign up for a mailing list to be notified of new free content when it becomes available.
Finally, there's etree.org. A LOT of artists give permission to allow the recording and distribution of their live performances. etree.org only offers "lossless" recordings, so you'll need to convert them into another format to use them on your portable media player. The good news is since these are lossless files to start with, you won't have the data degradation and conversion artifacts typical of say, converting a WMA to an MP3. It's more like ripping an CD.
All told, there's a LOT out there free of charge. The Kuro5hin article I link to below has even more detail.