Pretty much anything by Paramore cheers me up, I like to (although suck at) sing along with it

(Note the sig)
Whoever mentioned Snow Patrol above, I second that. I kinda was listening to a lot of them before I starting SI'ing so it's kind of extra emotional to me, although I try not to always tie it back to that. They're just awesome.
Also, although I've got to admit it's pretty triggering, Bleed Like Me by Garbage is really awesome. Maybe give it a listen IF you're feeling safe. I just like that it shows we all have problems and we aren't alone.