Ventura Highway - America (it's old, but slightly more obscure)
Going to California - Led Zeppelin (okay, not obscure but NECESSARY)
California - Joni Mitchell (Incidentally, the above song is supposedly about Joni Mitchell)
Losing California - Sloan
California One/Youth and Beauty Brigade - The Decemberists
In California - Neko Case (though this is not very upbeat. It's about being homesick for somewhere else while living in LA).
California - Unified Theory
Queen of Hollywood - The Corrs
Fountain & Fairfax - Afghan Whigs
Gone Hollywood - Supertramp
I Love LA - Rilo Kiley
Ode to LA - Raveonettes
Train - Goldfrapp