Our mashup Social graph for sites has been updated.
Lets you search sites associated with the given URL (e.g. other sites from the same author) as well as the links (recommendations) in the social networks.
You can directly set your URL and search type in the request too. For example:
mashable.com - more mashables
dzone.com - links to dzone
P.S. check out also:
Whois for Twitter
Whois for Facebook