It’s been an active 2011 for Greplin. In February, we covered the social search service’s public launch and, mere days later, wrote about its closing a $4 million venture round backed by Sequoia.

Since then, Greplin has been rapidly expanding the social applications it can search and index, adding Yammer, Highrise, and Google Contacts last month to its already healthy set of networks and services. On top of these, you can authorize it to search Dropbox, Twitter, Facebook, LinkedIn, Google Calendar, Google Docs, Evernote, Basecamp, and Gmail. With a single search query, sha-bang!, Greplin can search nearly your entire personal cloud for that address, contact, or invitation you just can’t seem to find.

What’s more, today Greplin is announcing the addition of a Chrome extension to its search presence, so that you can search your social data directly from your browser without having to go to Greplin’s website to login. Check out the extension here and Greplin’s widget in the image to the right.

Greplin employs the new Chrome Omnibox API so you can get auto-completed results, regardless of what site you are on. For those unfamiliar with Omnibox, it’s another word for Chrome’s search bar, which allows you to type URLs and regular old keyword searches into one unified place, rather than having to go to Google.com. Omnibox’s API, then, lets extension developers to make the tool even more powerful by adding their own keyword command, so that user can type a query prefixed by the keyword, enabling the extension to suggest potential completions and react to the user’s input.

The company also announced the addition of Aaron Sarazan (formerly at Spark Plug Games), who will be working on creating a native mobile app. Co-founder Robby Walker told me that Greplin is currently looking to beef up its staff, so all expert engineers looking to get involved with a hot young startup attempting to provide us with the “other side of search” should heed the call.

Walker said that Greplin will continue to add to its list of searchable social apps, with Basecamp and Salesforce among the services currently being offered in private beta. (And Box.net and Google Voice coming next.) TC readers can preview these by emailing support@greplin.com.