There are various forums that are Second Life-oriented. However "the forums" most often refers to the "official" forums on the Second Life website which are owned by Linden Lab and run by Lindens (as well as "Resident Moderators"). The forums are often regarded as "drama" filled, but some sections can be a good source of information as well. The "Linden Announcements" forum is especially notable to keep an eye on as most important announcements are made there.
On August 10th, Robin Linden posted on the Official Linden Blog that the forums will be refocusued, starting with the removal of “Bulletin Board�?, “General Topics�?, “The Sandbox�?, “Land and Economy�? and “In-world Political Science�? forums within a month, with some of the other boards to close later on. As she said in Her Post:
"We’ve decided to focus Linden energy on building out the Linden unified blog and planning for other www.secondlife.com and in-world communication options. Ultimately we want to see a richly supported community of Resident websites living alongside improved in-world social features as SL rises to its full potential."
No word has been given as to what other communication options have been announced. Reaction to the closing of a part of the forums was very emotional on both sides of the equation, with parallels being drawn to when The Sims Online closed their own forums. Also, activity in third party forums such as Second Citizens and SLUniverse's forums has skyrocketed in activity from people checking out forum alternatives.