(via Apple): Apple - MobileMe - News - Sharing Large Files with iDisk--Brian
We're pleased to announce that you can now use your MobileMe iDisk to share files with others simply and easily. 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.
The process is a simple matter of going to iDisk on me.com, selecting the file you want to share, and clicking the Share File button. This tutorial shows how easy it is.