There are numerous services popping up to help you keep track of your favorite browser bookmarks. From what I can tell from Alexa traffic, the top three are Digg, Technorati, and Delicious. It seems like there are new services popping up every day and it can be hard to keep with with how to let users add your bookmarks to their bookmark service. AddThis.com looks like it's trying to help.
AddThis has a list of all the current bookmark sharing services and also keeps track of statistics of how many users add and share a specific URL.
Danny Douglass has published an extension for BlogEngine.Net at Add Social Bookmarking Links To Your Blog that adds several of the most commonly used social bookmarks.
The icons from Danny's extension were from the Web 2 Icon set from FastIcon.com.
I took Danny's idea and added in links for favorites and e-mail.