I've been practicing a lot on this website back when I was learning the guitar, and I'm still using it today on stage:
http://www.karaoke-version.co.uk/custombackingtrack/
Loads of standards, from AC/DC to BB King, and you can customize the tracks online for your instrument (even lead or rythm guitar).
It's quite a high price for a backing track but it is definitely worth it!
