A comprehensive Bisset / Bissett website is a Canadian one, bissett.org where there is a comprehesive history and a selection of different Bisset tartans.
The family motto is “ABSICISSA VIRESCIT” meaning

“Though we be cut off (or hewn down), we will still grow green (or flourish)”

This moto is also depicted in the family crest, below is a picture painted by Avril Bullock (nee Bisset) depicting the shield hung on the cut tree.

There is a genealogy forum which has a section dedicated to the Bisset name, http://genforum.genealogy.com it serves as a point on the Internet to try and link sections of family trees.