Bits and bobs, essentially.
I've done posters for my uni course (and expect to be using it a lot more if I get this job I'm angling for - more on that if I even get an interview), for events within the students' union, and I was asked to do campaign posters at the SU elections, so there's an element of that.
I also use it as my standard editing software, and will typically use it to rustle up an avatar, or just crop a picture for my desktop, etc. Used it to create my twitter background, and to do artwork for bits of music I rustle up on bandcamp. Back when I had a blog, I used it to make a logo for that, and still use that logo for my music.
Oh, and I occasionally use it to make people on the internet laugh - whether that's people I actually know, or people on here.
FAO anyone who can't afford photoshop... there's a pretty decent clone on the internet, free access.
www.pixlr.com - almost identical. A little more primitive, but so much more powerful than MS Paint. Use it when I'm in a hurry. Cropping or fiddling with colours or what have you.