Many applications have the built-in capability to send emails. For example, you can send a document from Microsoft Word, a PDF from Adobe Acrobat, or photos from Windows Explorer.

The problem is that these don't work with web-based email, including Gmail.

gAttach! allows you to easily attach files to new messages in Gmail or Google Apps Mail.

All the features available in Windows that were once only available to your desktop mail-using friends are now available to all Gmail users.