This seems pretty obvious, but some Mac + Firefox users may appreciate it. I recently upgraded to OS X Leopard, and one of the things I really like is the stacks feature. This isn't a mind blowing feature, but as someone who doesn't like a lot of files on the desktop, but does like quick, easy access, it works quite nicely.
Safari automatically downloads files to the downloads stack, and I was irritated that by default FireFox downloads files to the desktop. As someone who tries out a lot of ...