If you're a Windows user you know full well the tight integration among Microsoft products that has made the operating system a little less than friendly when it comes to tying in various Web apps. E-mail in particular is one of those actions that will usually pop up Outlook or Outlook Express, forcing you to either install a third-party mail app like Mozilla's Thunderbird or go in and tweak your registry.
If you're a Gmail user, and looking to get that same level of integration in Office documents and elsewhere on your system check out gAttach (download). This simple program will append all your mail extensions, getting them to open up in Gmail instead.
One thing that's nice is that it'll simply tack onto whatever browser you've got open, or simply open your default one if you don't have it running. It'll also suck in multiple files at a time (up to Gmail's 20MB limit of course).
Yahoo mail users can also take advantage of a sister product called yAttach, which will do the same thing, although you can't have both installed at once.
See also: Set Web e-mail as default Firefox e-mail