Lot's of sites offer the capability to upload a File. There's usually an input field with a button and when you click the button, you get a file system browser that allows you to navigate to the file that you want to upload. Safari 3 has a great feature that makes file uploads much quicker. Instead of clicking on the button to browser for a file to upload, you can actually drag-and-drop a file onto this button and it'll show up in the file upload widget to be uploaded on the web page.