I listen to a lot of stuff kinda like that. At least in terms of mellow. I'll spill a few in hopes you haven't heard of them. They're all pretty common in my opinion, but really nice chill riding music.
Band of Horses
The Black Keys
Imogen Heap (same chick that's in Frou Frou with another girl)
Mackintosh Braun (Super synthed out vocals...i REALLY love their new album "Where we are")
Phoenix (Their newest album is one of the greatest releases of any artist ever IMO)
Slightly Stoopid (mellow chill vibes stuff)
Stereophonics - (check out the song "Maybe Tomorrow")
30 Seconds to Mars (probably the most charged stuff out of the group. I really like their first album.)
Hope I helped. All solid tunes. Got it all in my boarding mix along with 30 or so other groups. Best of each artist and I can hit random and ALWAYS get something groovy.