The pattern "movement" -- the wave of using pattern language and concepts to express process design and group behaviour strategies -- has had a hub since the early days.
This site is that hub. It has aged, though -- many of the pattern pages have been removed or are 404 :(
The original movement was concerned with bringing the concepts behind architectural patterns into software design, so most of these pages are about that. More recent patterns for Agile teams and organizational development are mostly other places.
It is an older wiki, so it takes a few clicks to get what you might be seeking. The site is also rich with history and quotes from pattern leaders, as well as patterns, of course.
Some good pages:
Pattern Index - "Each pattern describes a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice." -- ChristopherAlexander
Anti-patterns - "An AntiPattern is a pattern that tells how to go from a problem to a bad solution."
The Gang of Four and their Design patterns book, which has a lot of nifty patterns (right on the web page)!