del.icio.us is a free social bookmarking site which lets you log in, post a URL, a brief description and use ‘tags’ to organise and categorise your links and browse those submitted by others. It even generates RSS feeds of bookmarks for each user. On its own this is very cool, and a good way to keep track of bookmarks across multiple computers / operating systems / locations.
If you happen to be using Mac OS X, Cocoal.icio.us allows you to access and manage your del.icio.us bookmarks, descriptions and tags without having to use a web browser by talking directly to the del.icio.us API (once you’ve told it your username and password). It also features a built in browser preview window, so you can click on a bookmark and to check that you got the URL right etc.