HFS -- HTTP file server

From lifehacker:

All you have to do is run the application on the computer with files you want to share, then selectively pick files or directories you want to allow access to. In addition, you can even upload files to your HFS server from elsewhere. You'll need to set up port forwarding for port 80 on the computer running HFS and then either remember your public IP address (which may change) or assign a name to your home server (for free)...