Due to Google's deprecaton of the Social Graph API this script likely won't be updated to work with the new Twitter design.
OtherMes is a Greasemonkey script that adds icons to tweets showing the Twitter users' profiles on other social networks.
It's built and tested on Firefox 5 and Chrome Canary (what will become Chrome 13). It utilizes Google's Social Graph API to discover other profiles. It can be a Facebook account, a Google+ account or an about page on a blog.
Reinstall the script to get the updates.
By making sure there are links between all of your profiles marked up with rel="me" you should get them included when people indexes your social graph. If you can - make the rel="me" links bidirectional to make them more trustworthy.
Combine rel="me" with rel="author" relations to also tie your content in to the social graph.
Can't do a social script without doing a social dance - so here's the button you'd expect: