Although this is no longer maintained, it remains a good resource for IxD design pattern resources. This page contains information about resources related to pattern languages for interaction design (of which user interface design is a subset), and a few links to more general papers that may be of use to interaction designers. I also include some links to organizational design patterns, which I find hard to disentangle from interaction design.
A seemingly spottily maintained resource but interesting nevertheless. This site seems to promote the process of learning about and creating pattern libraries. You can find links to the following pattern-related resources: People, Events, Patterns, Publications, Tools and Other Resources
Formerly called the UI Pattern Factory...
From the site:
"Patternry is a resource for everyone who needs to design or develop user interfaces. It is a collection of Web design patterns which helps people solve common design problems when designing interfaces. Soon it will also be a community where everyone can share, create, and collaborate on design patterns. We are still in beta, so be patient with us."
Site that accompanies the book "The Design of Sites." From the site: "Design patterns solve recurring design problems, so you can use pattern solutions to design your sites without reinventing the wheel."
I find this site to be often breathtaking in its breadth and detail. This is how a patterns library should be done...if you have a ton of time, resources and money. Lots and lots of documentation and working examples.
This is a great resource that I think it newish in late 2010. Concentrated on search and discovery...or as the site itself says "...describes principled ways to solve common user interface design problems related to search, faceted navigation, and discovery..."
A pattern library that focuses on open-source design patterns (whatever those are). Has categories for Content Management, Information Organization, Input Forms, Navigation. A good resource and interesting site to explore if one is interested in a well-documented project.
last updated in 1999, this site appears to be Tidwell's site while doing her graduate work (she went on to write the seminal Designing Interfaces book). Still an amazingly well done and valuable resource on design patterns.