Windows/Mac/Linux: If you're interested in the idea of cloud computing and remote access to your files but are a bit paranoid about putting your data on some third party server, Tonido is a great compromise.
Tonido brings cloud computing home by using your computer as the storage server and host for the applications. Once you've installed Tonido, the only function the Tonido servers themselves perform is keeping track of your IP to make remote logins easier for you. Tonido has a juke box for remote media streaming, a photo organiser, a blog-like personal journal that has support for web clippings and Twitter integration, easy file sharing with Webshare folder management, and a workspace with calendar, notes, and task lists. In addition to making it easier for you to remotely access your files and work with them regardless of the applications available on the remote machine you're using, Tonido has a built in P2P service which allows you to network with friends and colleagues to share files and collaborate on projects.
The biggest downside of Tonido is it requires your home computer to be on whenever you're away, but if you're running an always on home server or if data privacy is a big issue, the inconvenience can be overlooked. If you'd like to avoid giving your data to third parties but would rather not leave your home computer on 24/7 for access, make sure to check out previously mentioned EyeOS, a cloud computing solution that you can install on your private web server.