Microsoft i'm Initiative

From Microsoft:

The i’m Initiative from Microsoft® makes helping social causes easy. Every time you use Windows Live™ Messenger or Windows Live Hotmail®, our free webmail service, we'll share a portion of our advertising revenue with the cause you choose from among our partner social cause organizations. Exactly how much will we share with our partner causes? Well, that's up to you and the growing masses of i’m Initiative users. The more messages you send, the more we give.

Now the small things you do every day, like e-mailing and IMing, can make a big difference.

Interesting concept but a limited number of causes to choose from (and a few animal testers among them):

AMERICAN RED CROSS
BOYS & GIRLS CLUBS OF AMERICA
NATIONAL AIDS FUND
THE HUMANE SOCIETY OF THE UNITED STATES
NINEMILLION.ORG
NATIONAL MULTIPLE SCLEROSIS SOCIETY
SIERRA CLUB
UNICEF
STOPGLOBALWARMING.ORG
SUSAN G. KOMEN FOR THE CURE

I haven't made the switch yet because changing email addresses is a big ole' pain in the butt. This, however, might incentivize me to do so even though it's kind of a rip off of Working Assets.