very useful links indeed. hope these sites stay on.I know there are sites with calculations for this, lets see if I can find them...
Bump: The first 2 are simple calculators. The last is more of an engineering and background sort of page.
http://www.garf.org/tank/buildtank.asp
http://www.bayoureefkeeping.com/pages/DIYGlassAquarium
http://www.fnzas.org.nz/?p=1732