The Dropbox File System

Email has become the virtual dumping ground for everything. People are expected to accept anything via email, not lose track of emails, accurately sort, manage and maintain a clean, proper reply thread on every discussion. The problem arises when you receive/send the same file from/to multiple people who make their individual changes (and often on outdated versions!).
Version control doesn't work in emails!

Dropbox has become the best replacement for attachments.

Why Dropbox could work well for you:

• easy to share files without any login required for the viewer
• easy to have a shared folder so that new files are automatically seen on the viewers' computers
• works seamlessly with the OS, no additional FTP app needed
• It's fast and reliable along with file version management and an optional yet excellent web interface

One of the unexpected benefits is that clients can see exactly what files are being worked on in their projects and when. This helps greatly with providing transparency over a project (more so when growl alerts are enabled). BTW, dropbox is highly secure for confidential files - in some cases more secure than many high-end email systems.