I generally pick one album and loop it. I skip certain songs though sometimes. Theres always that one track thats out of place and doesn't get played. Before I had an MP3 player the CD that was in my car for about 2 years straight was Alice in Chains - unplugged (until someone stole my cd player and took the CD with 'em, grrrr)
When I was in middle school on the bus it was metallica, metallica, metallica. Everybody in the world knew my obsession with metallica.
The past 3-6 months have been symphony x - oddysey.
Generally speaking, I pick an album, listen to that album and only that album for days, weeks, or months, then switch to something else. Often go back to previously looped albums.
My brother is big into music and often goes on and on about multitudes of different bands and such. When that conversation starts I feel more or less like a dumb rock with nothing to say. Talking about preferred music is one of the hardest topics for me to get involved in, unless the other person is into the same music. Unfortunately my music choice isn't popular.
At one point I had iTunes hooked up to some website which would track my music selection to find other bands to listen to. I never used the feature, but it still tracked my music. I was the #1 melvins fan by a large margin. I guess there was a time period where it was nothing but melvins for months on end.
I find it hard to get into new music as well. My friends find a new band and tell me about it saying this and that and blah blah blah. Could be great music, but compared to the FotM album being looped its nothing!