Ever since Apple announced their rehash of .Mac called MobileMe, one highly anticipated feature proposed to appear was absent from the iDisk feature set.  Until Feb.12th!
FINALLY, this feature helps make iDisk more of the killer app I'd hope it would be.  Any file located on your iDisk account, in the Public folder OR not, can be shared with anyone without needing to give them access to all of your files, or the annoying task of figuring out what the name of a link should be to a file in your Public folder. 

Now you can post files to iDisk and just send a link to your client,
even with a finite expiration date. 

But say you find it annoying that
you need to log into your MobileMe account in a web browser to use this
feature.  There's a cool little application that I've found useful, which I located back when the MobileMe file share feature was found to be just a myth.  Dockdrop just sits in your Dock.  If you want to share a file, just click and drag the file to the Dock icon, choose the method for posting the file, and after the file uploads a URL link to the file is placed in your clipboard ready to be pasted into an email.  It doesn't get any easier, folks. 
It takes a little bit of configuration, but once it is set up it's the easiest way I know to post files to a server and share with others.  It works with your FTP, Flickr, WebDAV (iDisk), or SCP server of choice.  Their Demo Video will make it clear how slick this really is...