A1 Business Forums has been around since Feb 2008, and has steadily grown both in members and traffic since that point. At work, we've been responsible for doing the design and continual support of the vBulletin forum, as well as assisting in the initial setup. Aside from that, I've also been an active member, racking up around 2,000 posts since I last checked.

Registration is simple and free!
It was initially setup by Ray as a UK based forum where small business owners could go to get helpful advice and support, as well as have somewhere to have relaxing chat & banter. The forum covers a wide range of subjects from Accounting to Search Engine Optimisation and a forum to get quotes from a vast number of suppliers who visit the forum. Since it's conception, I don't think Ray, I or anyone else imagined it would reach the stage where within 8 months, it has over 3,000 active members and 80,000 posts!
Due to rising commitments at work, Ray offered to sell the forum to me and one of the other admins, Phil over at Open Mind. We naturally jumped at the chance, having both had experience in running large forums (fora?) and with both of us running successful small businesses, it's definately something that interests both of us!
So, the business forums are now under new management, and we're both very excited with the plans we have for the forum in the coming weeks and months!
I try not to post work-related stuff here, but I know several small business owners read this, and I'm sure you'd benefit from the wealth of knowledge at the forum - so go sign up!