Visualisation Patterns is amazing. Not the greatest in terms of presentation (which is ironic), but the information that is contained here is GREAT.
What this is about is identifying diffferent patterns. Patterns are a method to capture, document, and share recurring HCI problems.
Want the specific definition of a pattern? As according to Borchers? He's got it.
Want to know about Visual Seperation (aka Occlusion)? He's got info on that as well. (I just wanted to type and say occlusion. It's a fun word) Small Multiples? Check. Datatips? Check. And so on and so on. And those are just the Structure Patterns. He's also got a whole section on Interaction Patterns (Level of Detail, Dynamic Queries, Bounding Box, and so forth).
I even like the result page for each of these patterns, as it follows the definition (attribute listing) that he gave in the introduction. These attributes are: Title, Context, Problem, Forces, Solution, Examples, and Related Patterns.
This is a great, great resource. Lots of really interesting stuff in here.