Luckily, for the adventuresome, it's easy to add this functionality to your favorite web browser by creating a "bookmarklet".
Just right click and save the following link to your favorites or bookmarks or links toolbar. You'll have to then EDIT the saved URL because you'll want to put the appropriate values in for TO, CC and BCC.
And if you use the YAHOO EMAIL link, you'll need to replace the server number (f415) with your server number. And be aware, this number will change on you from time to time and the bookmarklet will stop working until you fix it.
Email Bookmarklet Version 1: Yahoo
Email Bookmarklet Version 2: Standard mailto:
Update: To make Yahoo mail your default email application, install the application and follow the directions at one of these pages. No more need to modify your registry by yourself!