Located in Tunbridge Wells, Kent, UK. Not to be confused with the other Forum in London. For the sake of anal detail, the address is:
Originally a block of public toilets (the biggest in Europe for a while) built in the 1920s, it was leased from the council in 1992 by four locals who thought it would make a nice music venue. On January 15, 1993, The Forum officially opened with headline act, Foreheads in a Fishtank. The first band ever to play at The Forum were their support band, Joeyfat.
Since 1993, The Forum has been host to roughly twelve bands per week, and developed a dedicated fanbase and community. It is especially popular with the mid-teen crowd who perhaps also appreciate the somewhat lax approach to underage drinking and recreational drug use. Naturally it is dominated by local bands who tend (at the time of writing) to be punk, skacore, emocore, or nu-metal (see: Current musical trends I really hate).
However, The Forum also has a great record of hosting up-and-coming bands before they make it big. Examples include: Green Day, Oasis, Coldplay, Feeder, Muse, Placebo, Ocean Colour Scene, Stereophonics, Travis, Reel Big Fish, and many more. At the other end of the spectrum are the numerous once-huge acts who have dropped back down to the level of gigging at The Forum afterwards (Chumbawamba and Reef being the best examples).
Websites, Fanzines, etc.
The official Forum website is currently located at: http://www.users.globalnet.co.uk/~twforum/ (please /msg me if that URL is out-of-date). There is also an excellent unofficial website called The Holy Toilet (http://www.holytoilet.com) which hosts the online version of Forum Fanzine, "BLAM!".
The official website is the place to check dates, book tickets, etc., while The Holy Toilet is a more subjective look at the music and the community.
Various "battle of the bands"-style competitions have been organised in the past. Now it has all been formalised with the introduction of The Stable. The Stable operates over several rounds, with league tables for each round, and the top half of each league table going through to the next round. It is very popular with school bands who abuse the audience voting system by inviting all their friends. The organisers don't care about this because it means more money for them. Fortunately nobody takes The Stable too seriously, so it's a great way for local bands to gain much-needed exposure.