I've been a little addicted to that song as of late.

Me:

"Psychotic Reaction" by the Count Five always puts me a in good mood. I think it has something to do with the fact that the lyrics start out with "I feel depressed, I feel so bad...", but then the rhythm and melody are so happy and sound like such a party that even if you are depressed you're somehow just whisked away from it all.

"Till the End of the Day" - The Kinks
"Go!" - Tones on Tail
"Maybe the People Would Be the Times or Betwen Clarke and Hilldale" - Love
"Sweet Thing" - Van Morrison

TRex
Burning Spear
Sam Prekop and/or Sea & Cake
Ella & Louis
Motown

I have a lot of oddball cover tunes that serve just this purpose

For example a version of "Rain drops keep falling on my head" played completely on the cuica by Trio Mocoto. so awesome.

T. Rex
The Kinks (mainly Village Green and Arthur)
Mercury Rev (first 3 albums)
Flaming Lips (early '90s stuff up to Clouds Taste Metallic)
Deerhoof
Animal Collective
Mouse on Mars