My workshop soundtrack wanders all over the place, but recently I've been queuing up a lot of Leo's awesome metalized covers of songs:
Or just cool instrumental surfy stuff like Los Bitchos
And had a Serg Tankian evening a while ago (lead singer for System of a Down doing some great solo stuff)
And when nothing seems to go right, pulling out this one is great for stress relief and putting a smile back on! (you need to listen at least to the first chorus)
And there's always the excellent one linked in my signature below for a chuckle too!