For all of you who like the mashup thing you should give some of these a shot. I've wasted a few hours scouring the internet recently (since I have nothing better to do) and found some I like. The first one's by Ozzy, Kelly and Pink. The next one's a pretty simple mash by Imogen and U2. Finally I'll let you sort out this mess of alternative ballads from the last 10 years or so.
Don't hate me for being such a softy for pop (chris and eric).