CloudKafé is a free, attractive webapp that helps you search through all the documents, photos, and videos you have scattered across the web.
Once you create a CloudKafé account, you can connect it to your various cloud services. The site supports major players like Dropbox, Evernote, Facebook, YouTube, Google Drive, and more, so most everyone should be covered. Once your accounts are connected, you can search them all with a single search box, and get instant results organised by file type. The concept and execution is similar to previously-mentioned Mac app Found, but as a web app, CloudKafé will work on any platform.
As a relatively new service, CloudKafè isn't perfect. For example, I couldn't get it to pull in my Facebook photos. Still though, it's worth checking out if your digital life is spread across the web.