YouSendIt is an online service for sending large files across the Internet. They have expanded their service by offering to the public a free downloadable plug-in that allows files and pictures to be uploaded directly from Photoshop.
The plug-in of course requires that you have a YouSendIt account first. You have a choice of signing up for a free account that allows transmitting up to 100MB maximum file size (then pay $6 if you need to send up to 2GB), or sign up for the paid accounts for $20 or $30 a month.
It also requires Windows XP w/SP2 (no Macs yet) and Adobe Photoshop CS2. The plug-in may be downloaded from here.
There is of course another service you may try, www.megaupload.com, where you can send up to 500MB absolutely free, not directly from Photoshop perhaps but still directly from your computer.