Writing good XSLTs is heavily experienced-based. I also did not find any XSLT-patterns resources until now.
Mailing list
I learned XSLT on the Mulberry XSLT list. That's a very good resource with the best XSLT-writers offering their help: Michael Kay, David Carlisle or Jeni Tennison, but learning from a mailing list, i.e. by other ones' use cases, is of course very time consuming.
Books
From that list I know that Jeni Tennison is a very good explainer and I heard her books are good as well. She has one book for beginners and one for advanced users. Michael Kay's reference is also recommendable.
FAQ
Furthermore there is a FAQ on XSLT maintained by Dave Pawson, which is more or less a Best of Mulberry XSL list, but you need to know what to search for.
Specs
And not to forget the specs on XSLT, Namespaces and XPath, they are readable and not that long.
Tutorials
An excellent XSLT Tutorial in several languages on ZVON.org
Patterns
Helpful XSLT Patterns (German only) on http://infos24.de