I implemented an AddThisButton and used it in the blog. I've created a site setting for the addthis account and it can also be overridden in the blog settings in case you have multiple bloggers with different accounts.
The control can also be used in layout.master so it appears on every page of the site so that even non-blog pages can be social bookmarked.
As you can see now on this site.
The new code will be in svn trunk by tonight.