This site has a lost of forum posts you can learn from. Reading them yields different approaches to a problem you might not think of yourself. SQL Saturday events are a great free events. The schedule is at http://www.sqlsaturday.com/. I don't know where you're located, but you may have a local PASS chapter near you where you can attend presentations.

Of particular interest to me:

Strings, Splits and Such

If you haven't done so yet, check out Jeff Moden's article on Tally Tables at http://www.sqlservercentral.com/articles/T-SQL/62867/. You'll find new uses for it constantly.

The next one to check out is the DelimitedSplit8K article at http://www.sqlservercentral.com/articles/Tally+Table/72993/.

Dwain Camps has an article on Pattern-Based splitting at http://www.sqlservercentral.com/articles/String+Manipulation/94365/.

Books

For a wide variety of topics, check out the SQL Server MVP Deep Dives. There are two of them and you can find them on Amazon.

Grant Fritchey's book on Execution Plans is excellent and is available for free at http://www.sqlservercentral.com/articles/books/65831/.

In fact, there are a lot of good books listed at http://www.sqlservercentral.com/Books/.

I could go on an on about different authors, but there are an awful lot of them.