Ubuntu One: free personal storage.

Ubuntu One is so far one of the best services of this type I've seen. It allows you to upload files from your computer, download them on any computer, and even share them with your friends, if you want so. A free Ubuntu One account allows you to have up to 2 GB of files uploaded, and, if you need more space, you can update it up to 50 GB for a $10 fee/month. You don't need any advanced knowledge in order to use this service, as it is simple and also fast.

Go and start using Ubuntu One: https://one.ubuntu.com/ (if you don't have Launchpad account, select "Subscribe")

Please note that it worked for me only under Chrome and Firefox (latest versions). Opera 10.50 wasn't able to display my files, and IE 6 displays everything wrong (I haven't tested it on IE 8, it might work into it).

Cloudo - Your virtual desktop OS.

Cloudo is a free internet application, which allows you to take everything from your computer with your, wherever you go, without carrying physically anything with you. It's practically a virtual PC. You access it via a username and a password, and you can upload, download and view different files on it.

It has basically a few applications and games available, but its secret consists into a XML editor. If you known XML, you can make anything using this markup language. Additionally, Cloudo offers an word editor, text editor, mail client, calendar, and even a contact manger. So, you can use it even you don't know XML at all. You can upload any file from your PC, and view them or download them anywhere on the earth. It's really simple. And free.

Try it: http://cloudo.com/