MXTabs is always my first port of call for guitar tabs, though I can't say how good they are for bass tabs.
I need the bass tabs to funky town by KC and the sunshine band. I looked all over teh internet bu found nothing.
Seenas mxtabs has been taken over (for me at least - it might be a browser hijack ), this is the next best thing as it searches through all of the sites mentioned above + more for tabs.
I think MXtabs has been taken down by the owner until a legal issue gets sorted out. Basically some music industry people decided that posting tabs is illegal, and that the people owning the sites should be put in jail Edit: here is the story.