FileChute from Yellow Mug Software has been kicking around for awhile, but has been pretty much under the radar for most people. Some of our readers mentioned it when we reviewed YouSendIt last January. FileChute is powerful because it can send any size file, as long as you have space on your iDisk, FTP site, or WebDAV web server.
Using FileChute is a really simple operation. Just drag a large file (or a small one) to a target on the application and it uploads that file, allowing you to specify if you want to zip it and provide a short URL. FileChute will automatically create an email with the URL in it, ready to send to anyone. I take a lot of astronomical images, and they won't fit in an email at their native size. So when I want to share the high quality versions, onto FileChute they go and the person I send them to only has to click on a URL to download the file, or see it displayed in a browser, depending on what type of file you have sent. You can send applications, movie files, anything really.
Before Leopard came out Apple was making some noise about providing a similar feature in Mobile Me, but it never appeared, and in the messy launch of Mobile Me I think it was forgotten.
Recently, Yellow Mug added an iPhone and iPod touch version of the application, and it can see your files stored on the web server of your choice, and initiate a file transfer just as if you were sitting at your desktop or laptop mac. It's free for FileChute owners.
Sure, there are lots of ways to transfer files, but this application makes it drop dead easy. I find myself using it several times a week. It's the kind of thing that should be built into the Mac OS, but you can have the feature now for less than 20 bucks.