The LSL Wiki, located at http://lslwiki.net/ , is also sometimes known as "Bad Geometry". "Bad Geometry" was an error message that used to happen very often when changing prim shapes, and could result in invalid primitive shapes that could even crash the sim. There is also a LSL Portal created by Linden Lab on their wiki that is used in the client.
Historically, the only source of information on how to write proper scripts was a single HTML file included with the client that was a bit scarce on details. Residents had to supplement that with their own findings, spread through word-of-mouth, and so they were often found asking each other all sorts of scripting questions in-world or in the forums.
Jake Cellardoor eventually created the first alternative source of info in the form of a CHM file where he included both the official documentation and resident contributions. New versions were released infrequently (only when there were actual language changes), and development of this documentation was centralized. The last CHM produced by Jake consisted of a compilation of articles from the (then new) wiki.
The wiki was founded and largely developed by Catherine Omega, with hosting space provided by Bel Muse at http://badgeometry.com. A while later it fell under a "denial of service" attack that rendered it unusable for a long time until Linden Lab generously offered to host it on their own server.
The LSL wiki remained on LL's servers until an exploit in the Tiki wiki software was used to gain access to user information on the same servers. After the attack the wiki was taken offline indefinitly much to the dismay of scripters. Meanwhile, Catherine Omega had been in negotiations to once again host the wiki privately, out of want to be able to properly administer and update the wiki software (things that LL didn't have the time/want to do). Weeks after the attack Catherine was able to get a backup of the latest state of the LSL wiki and host it on her own server with the domain of lslwiki.com.
Currently the former link for the LL hosted LSL wiki points to a somewhat dated mirror. LL has since developed their own LSL Portal with a design similar in style to the LSL Wiki's front page. This portal contains much the same information that the LSL Wiki does. The Help Menu and LSL Editor in the client both use the LSL Portal now.
Catherine Omega meanwhile ran into some issue with her hoster and had to switching hosting. The domain lslwiki.com became unusable as well, forcing the LSL Wiki to use the new domain of http://lslwiki.net. The LSL Wiki is currently back up and running successfully.