Many colleges and universities have faculty development centers (sometimes they are called "teaching excellence centers") with full time staff who serve as resources for professors and graduate teaching assistants. Their professional association is the Professional and Organization Development Network. Many of these centers have outstanding websites with a wide variety of useful material.  Some of TΦ101's favorites are:

• The on-line Teaching Tips Index  from the Honolulu Community College is one of the best organized sites that we have seen, with links to readable resources on many teaching questions.
• Kansas State University publishes the IDEA Resources, including theIDEA papers.  These short, readable essays digest the research and give practical guidance and tips.  
• Brown University's Sheridan Center includes a handbook on assembling a teaching portfolio.
• The University of Minnesota Center for Teaching and Learning has interesting tutorials on subjects such as active learning, using PowerPoints, lectures, and managing conflict in the classroom.
• Harvard's Derek Bok Center has lots of resources, we especially liked how well it is organized. 
• Notherwestern University's Searle Center has a good resources page, with annotated bibliographies on various teaching topics. .
• The University of Michigan's, Center for Research on Teaching and Learning is a giant in the field, not surprisngly it has a lot of good materials. 
• The University of Buffalo Teaching and Learning Center's resources page includes a discussion of strategies for large classes.
• The Center for Faculty Excellence at the University of North Carolina has a series of publications called For Your Consideration, covering topics from the first day of class to student evaluation of teaching.
• We also liked the resources page developed by the Vanderbilt University Center for Teaching. Here, as with the Honolulu Community College site, all of the topics are written in a single voice.
• Clemson University's Office of Teaching Effectiveness and Innovation has many resources including some excellent material on learning styles.  
• Princeton University's McGraw center publishes The Scholar as Teacher, a series of brief tip sheets on teaching topics.
• The University of Delaware has a lot of material, but you need to keep scrolling down the page to find general resources).
• The Center for Instructional Development and Research at the University of Washington has a some helpful resources on writing exams.  
•  Among many other things, Wabash University's center-site also has some good links on student portfolios.  

In developing this list I have drawn heavily on Peter Filene's list of teaching center resources in The Joy of Teaching (Chapel Hill: University of North Carolina Press, 2005), pp. 155-156.

Update: February 10, 2010