When I get into a band, I really get into them. I can listen to a single band for years, literally. It won't be the only music I listen to, but it will be 95% of it. These phases started promptly in high school. Here I'll try to document the phases, as I can remember.

High School, Freshman and Sophomore Years
Mainly Nirvana. I had the hair and started learning guitar, and the first song I learned when I started getting guitar lessons was "Polly". They were an incredible band, Kurt Cobain was my hero back then. Moreso, they were the ideal band to learn guitar to, as Kurt wasn't a soloist like, say, Alice in Chains guitarist Jerry Cantrell. He played chords that were not usually played together, and put a hard distortion on them. All I had was a lousy classical guitar back then, but Nirvana sounded divine on it.

High School, Junior Year and most of Senior Year
Cracker. But they weren't dominant. Usually a phase for me is listening to one band 95% of the time, but this one was listening to only Cracker 50% of the time, but then I was listening to other bands like Pink Floyd, Grateful Dead, Phish, Led Zeppelin, [more as I remember].

End of High School, First year of College
Sublime. Although at this point I only had 2 of their albums and no computer. By now I could play Santeria even really drunk, and the solo. I also got more into Jimi Hendrix, and had learned "Red House", my first real blues song on guitar.

College, Year 2
This may come as a surprise to a lot of people, that someone like me can like a group like this, but I was totally into the Insane Clown Posse. I thought they were hilarious and made a lot of friends that year because I would blast them out of my dorm room.

College, Years 3, 4, and after
I got back into Sublime. By now I had all of their albums and just loved how Bradley played guitar and sang, and the bass lines and drums, and everything hiphop about it. Reggae is a big influence on me still.

2002 - 2004
I have no frame of reference for these years like "College" or "High School"... That's when time starts to fly. But those were the "working years" I guess. During this time I found the greatest guitarist and biggest influence on my music, Stevie Ray Vaughan. I bought all of his albums at one time off of Amazon.com. 10 of them. I also bought 2 DVDs and the SRV Signature Fender Stratocaster. He can just play. (What movie!?)

Present Phase
Back into Cracker bigtime and I can't put them down. They are all of my favorite albums.

Honorable Mentions
Other bands that I didn't quite get into a phase with, but really close to it, are bands like Bob Marley and the Wailers, Candlebox, The Doors, Grateful Dead, Jimi Hendrix, Verve Pipe, Eminem, and I know I've forgotten some so I'll edit it later.