Yahoo has really impressed me with their change from "annoying portal with too many links" to "doing lots of cool stuff and telling people how to use it too". Their developer network is a great resource for both just learning about a language/tool/design pattern, as well as how to leverage really deep and useful Yahoo resources within your own application.
Providing these resources is definitely in their own interests, such as Cache Yahoo! Web Service Calls using Ruby, but is also just a great service to the community. Their Gallery is also a good place for interesting sites and project ideas.