Mac: Google Docs is great for storing and editing documents in the cloud, but if you'd prefer a desktop alternative, then Collections is a new Mac app currently in beta that's worth checking out.
Collections isn't much more than a web app container for Google Docs, but if you manage a lot of different Google accounts, or you just don't like working in your browser, then it does the trick. The handiest feature is the support for multiple accounts. Just type in your Google info and all your files across multiple accounts are immediately accessible. You also get the same offline editing support you would with the Google Docs web version. The beta version of Collections is a free download from the developers site.