Greplin indexes data you store in the cloud and provides a quick and simple search to let you find what you're looking for.
You can index a lot of popular services, such as Gmail, Facebook, Dropbox and LinkedIn. While most services are free, a pro account is required for services like Basecamp, Evernote and SalesForce.
Once you start adding services, Greplin gets to work on indexing all your content and sends you an email when it's finished. You can always add more sources to Greplin later on and can remove indexes you decide you don't want anymore. When Greplin finishes indexing for the first time, you'll be able to search through all your stuff from a really simple search box. By default it will provide results from all services, but a little drop-down on the left of the search bar will let you filter your results.
Greplin is a free tool for most of what it indexes, but you can upgrade to a pro account and add anything for $US5 per month (or $US45 per year).