Delicious
A red letter day in the history of the Internets: I now have over 500 bookmarks on del.icio.us.
About
del.icio.us for those of you who aren't familiar with it is an online social bookmarking website. Essentially what del.icio.us does is it allows you to save your bookmarks onto its website instead of local on your computer like a browser does.
Another cool feature is it can tag bookmarks with words you define. For example you might tag www.nunit.org with .NET, Testing and Tool because it is to do with .NET development, it is used in testing and it is a tool you download. These tags then become very useful when searching for a bookmark. You can use them to filter you bookmarks, which is quite useful when you have over 500 [:)]
Why I Like It
I started using del.icio.us about 2 1/2 years ago and while it hasn't revolutionized my life and brought fame and fortune (yet...), its improved the way I work. When I encounter a problem I know I've solved in the past, I always check my bookmarks. Chances are I had googled the issue and then saved a webpage with the answer. If a webpage is there, tag filtering makes finding it a breeze.
del.icio.us is also useful when you work on multiple computers. Bookmarks created on my work computer are available on my home computer and vice versa. Using del.icio.us also means you don't need to worry about losing bookmarks. If my computer needs to be rebuilt I can just reimport my bookmarks from the del.icio.us website once I am back up and running.
Browser Integration
A number of Firefox extensions allow you to access del.icio.us bookmarks directly from the browser UI. del.icio.us has an official plugin that completely replaces Firefox's builtin bookmarks with del.icio.us bookmarks. Personally I prefer a third party extension called Foxylicious. It is a lot less invasive and works side by side with any existing Firefox bookmarks. All you do is point it at a bookmark folder and then it simply creates a new folder inside it for every tag you have and then creates bookmarks in that folder that belong to that tag. Foxylicious also adds a menu item to Firefox for quickly adding new bookmarks.
Final del.icio.us tip
If you can't remember where the dots go in http://del.icio.us, try http://www.delicious.com instead.