Besides just providing online storage with your MobileMe account, iDisk now comes with a “new feature”:http://www.apple.com/mobileme/news/2009/02/sharing-large-files-with-idisk.html that lets you share files stored in your iDisk easily.
bq. Instead of attaching a large document to an email and hoping it’s not too big to be received, you can place the file in your iDisk and use the new Share File command in the iDisk web app. It lets you send your friends, family, or colleagues a link they can click to download the file directly. You can password protect the link if you choose to and even set how long it will be available.
Slowly and surely, Apple is giving more features to MobileMe that hopefully will make the service worth the S$148 you pay for having it.
Have a look at the “tutorial”:http://www.apple.com/mobileme/tutorials/#idisk-share in case you aren’t sure how to do that.