I have the fret board off of a bass guitar, and wondering what type of glue I should use to glue it back on. I removed the fret board to work on the truss rod, which was rusted right into the wood neck, and the adjusting nut hex cavity was stripped. I did get the rod out, and tig-welded a new adjusting end for it from a socket head cap screw and cleaned the slot for the rod etc. I'm about to glue it back together and wondered about the glue. 
Tightbond. Nothing else, unless you want to try hot hide glue (which you don't). Please note, I did NOT say
Tightbond II,
Tightbond III, and I'm not talking about the hide glue that comes in bottles, but the stuff that comes in granular form. Hide glue is marginally better, but trust me, you don't want to use it. Really, I mean it. Its not that hard, once you get used to it, but it takes a long time to really get used to it. Use Tightbond.
(All that being said, any basic wood glue would be fine, but Tightbond is the most readily available, and because it tends to sell well, the bottles tend to be fresh, which is really important. Don't use it if it is past it's expiration date.)
Whatever you do, don't even think about using any form of epoxy. Just don't. You deserve what you get if you use epoxy.
Epoxy has absolutely NO place in guitar repair, and almost no place in guitar building.
It is the root of all evil in guitars, and if you even think about using it I will curse you to hell forever! Don't mess with me on this one.
And the only reason I'm joking about the hell thing is because, as an atheist, I don't actually have the ability to do so. If I could, I would.
Gabriel