I just found out about ID3 Tag editors!!! These are meta data editors for audio files. With these you can add album art to tracks, edit the artist, title, or genre and much more. There are a couple free ones floating around. Remove those nasty unkown labels in your audio player and spruce up your files!
iTunes has limited ID3 editing capability. If you want to really do it right, then I would recommend dBPowerAmp Music Converter, which comes with an advanced editor which integrates into Explorer, or in a separate app. You also get the best highest quality music conversion too. Great app, inexpensive, and well worth every penny. It’s especially useful with their free plugins, for making demo versions of your full length tracks. You can downgrade bit depth and stuff and select a starting and ending point and an exact length for the sample.
I use Windows, so I can’t say what works good for Linux or Mac. Although I had found some decent apps for those before when I tried those OSes. I just can’t remember what they were. Lifehacker often makes posts with nifty things for Mac and Linux if u want to try searching there. And most of those tools are free.