I just discovered this indie label, called Friendly Fire Recordings. They only have 3 rock groups signed, but they are really good, especially Asobi Seksu which are the big stars of the label. They all have their music on iTunes but the label and the groups give away some of their songs as freely downloaded mp3s.
Update 2: These 5 alternative rock groups are very good too. To listen to more of their songs you can make a search on google to find their respective myspace pages.
Update 3: Band of Horses is now one of my favorites. Their song “funeral” is very well done.