Tuba News
Pretty Self-explanitory too, a site with all sorts of articles about tubas and tubists, it also posts classified ads, all the stuff you'd have in your standard newspaper and it even had some pretty good stuff to download too!
Tuba-Euphonium Press
A place to purchase music for Tuba and Euphonium
Tuba Christmas
Honestly, I could not make a link page without putting in a link for one of the greatest events known to man, Tuba Christmas. From small quartet, to ensembles of over 500 tubists, this is one of the most beautiful things ever.
How about some collegiate Bass links?
California Polytechnic State University
University of California, Berkeley
Here we go with Notre Dame Band sections: