Yahoo! gets social
To be sure, some of the bigger sites are missing from here - no Digg or Reddit, no Delicious, no Flickr (even though Yahoo! owns Flickr).
All you have to do to add these is to head to your Yahoo! profile, click on "Updates" and then "Share More." Choose the sites where you have accounts, load up your info and presto! Your social media profile is shared in yet one more place. You can control who gets to see these updates through the (logically named) "Manage my updates" button on the settings/updates tab on your profile.