I have been a participating member of dBforums.com for years, but I have overlooked promoting it here. dBforums is an excellent resource for discussing database server software; data access, manipulation and batch languages; PC based database applications; and general database subjects. Every major product is covered by the forums.
I am particularly fond of the gang that hangs around the database concepts and design forum. I have participated in many design discussions there. I remember once helping a Malaysian DBA with the design of a database for a DNA sampling device. The members are diverse and the help talented.