I just started using Dropbox. I know a lot of people use it already – but I’m going to convert those who don’t with this post.
You sign up to Dropbox and download the tool, then it creates a folder in Documents called “My Dropbox”. Any files you put in there are automatically uploaded to their site.
If you install DropBox on another computer and sign in with your account, those files are automatically downloaded. That’s cool, but it isn’t what I use it for.

Inside “My Dropbox” it has a folder called “Public”.
If you put files in here they’re accessible to the public via a URL. I don’t think people can browse all your files in a directory, but they can access them if they know the address. This proves to be pretty useful.
Say that you want to upload a picture so that you can post it on the forums or wherever. All you have to do is save it in this folder. Then it’s then automatically uploaded to Dropbox. Then all you have to do is right click in the picture..
And you’ve got the URL of the picture in your clipboard.
This saves me a lot of time. When I wanted to post a picture from photoshop before I’d have to save it somewhere on my hard drive, go to filesmelt or imageshack etc, browse and find the file, upload and copy the URL. Now it’s just like linking people to files on my hard drive.
By the way, it isn’t just pictures, it’ll take any file want to link people to.
There’s a lot of other stuff that I have no cause to use. You can share a folder with someone so they can access your files etc.
Long story short, it’s kewl.