Our mashup Info from Twitter has been updated. It lets you pickup from the social graph other resources, associated with the given twitter account. It is a dead simple way to discover who is your new follower and who you to follow to in Twitter. Whois for Twitter.
You can directly type a name for twitter account on the mashup's page or pass it as a parameter. For example;
Also here you find an appropriate bookmarklet for this service.
P.S. check out also Whois for Facebook