Even the best social media site or wizz-bang collective intelligence Web 2.0 application has to adhere to some basic website usability principles. Here are 25 website usability points to inspect your site against. Very useful!

A few examples:

Section III. Navigation

Once people generally know who you are and what you do, they need clear paths to the content that interests them. Information architecture is a huge topic, but these points cover some of the basics.
12. Main Navigation Is Easily Identifiable
Almost every site on the web has had a main menu since the first browsers came on the market. Make your main navigation easy to find, read, and use. If you have two or more navigation areas, make it clear why they’re different.

13. Navigation Labels Are Clear & Concise
Don’t say “Communicate Online With Our Team” when “Contact Us” will do just fine. Your main navigation should be short, to the point, and easy for mere mortals to grasp.