There are plenty of sources that list the distances of various stars from Earth, but does anyone know of a source for looking up the distances of stars from one another? If not, I may have to dust off some spherical geometry that I would rather leave in its rusty box.

Specifically, I need to know the distance between Tau Ceti and Van Maanen's Star.

Update:  I found the specific answer I needed—Tau Ceti and Van Maanen's Star are 6.2 light-years apart—but I'd still be happy to be pointed toward a more general resource.