Web 2.0 List of Web 2.0 Application Links is great collection of Web 2.0 applications, listed by topic/type. Types include audio, blogging, bookmarking, calendar, collaboration, knowledge, multimedia, news and many more.
The site is plain white with the links and a very short description making it very easy to scan. You can also search for applications on the site.
This is a great resource for anyone who is looking for new apps to try or needs an app for a specific task.