I hardcore stan for everyone in my sig, though it's not really that difficult since they all basically do nothing (and Gaga is heading that way soon ) besides release an album every few years/decades, take their kids to school, etc.
I stan for lots of others too, just not quite as intensely.
Yes, though Gaga is my main bitch. Britney used to be, but ever since i found out about Gaga in early 09 she made me stan hard. I stan for Demi, Selena, Florence, Mariana, Ke$ha, Rihanna, P!nk, Ariana, Beyonce and Katy.
Beyonce and Mariah are like my "big" ones.
There are A LOT of other artists that I love but I don't really "stan" them, more of just a super-fan. For example: I listen to more Phil Collins than anyone else but I don't post/blog/tweet/stalk him or anything like that. I just love his music.