Not exactly "head-banging" music, but upbeat and good to work out to:
Gaelic Storm
Leahy
Fiddlers 3
Stone Soup Band (at least the songs I've heard)
2011 Surly LHT
1995 Trek 830
Shinedown
Days of the New (slightly older since they've gone separate ways)
Linkin Park
and a little different, not nearly as rock, but fun none-the-less:
Guster
My new non-farm blog: Finding Freedom