A great source of information about your MGB. You can be pretty sure that any problem or job you are planning on doing has been sorted by some other owner who is a member of one of the many popular MGB relayed forums.
MG Experience a great forum free to join with a wealth of information from owners across the world.
MGB Register not the most popular
MG Enthusiasts BBS Forum also has a lot of good information
MG Car Forum again not the most popular but with loads of info
MG Owners Club forum only for members