Doo is an automatic document organiser that finds files on your hard drive, in Dropbox and even in your email. On top of that, it'll take all your documents and sync them to the cloud and across multiple computers.
We're not without document syncing options these days, as we already have the wonderful Dropbox, plus both Google Docs and InSync for Google Docs, but Doo takes a slightly different approach. It's not designed to handle every single file on your machine, but rather any kind of document. And on top of sync, it organizes everything automatically for you. The downloadable app, for Windows or OS X, sorts your stuff in several ways. There are multiple options for browsing documents chronologically, but you can also find things by person, company, location, file type and a variety of labels. Of course you have the option to search as well. You can manually organise documents by project, too.
Doo is still in beta so you'll want to keep that in mind. Currently it is available for Windows (8) and OS X. Apps for iPhone/iPad, Android, and Windows Phone 7 are underway so you'll have full access on your mobile as well, but you can always access Doo from the web in the meantime. If you've got a mess of documents you want to keep organised without putting in a lot of time or effort, it's worth a look. You get 2,000 documents for free, but premium pricing is underway for people who need more and want bonus features like client-side encryption.