Writer's Block: Listen to This
The PaperChase: http://www.youtube.com/watch?v=zMwhrMA-jYo
The Knife: http://www.youtube.com/watch?v=5mkicED0zMI&feature=related
Foals: http://www.youtube.com/watch?v=PGrZkUQ6_r8
Does It Offend You, Yeah: http://www.youtube.com/watch?v=I8mErQG6hxg
this could go on forever. Of course, it would really depend on the friend and what their musical taste was to really make some good recommendations...