Here are two good options:
1 - Download and install Dropbox (Free, 2GB space) and any files you put in your Dropbox folder will sync across all your computers instantly. It also saves different versions of files and will allow you link to your file for downloading. It also has an online interface and iPhone application.
2 - Download and install Gmail Drive and make a separate Gmail account for storing files. It will show up in My Computer in any computers you install it on (free, ~8GB)
Personally, I prefer Dropbox because it's easy to link to files and the consistency and revisions features are great.