Sharing Outlook calendars online with friends
At last! I have been waiting to do this for ages and hadn't spotted it in Outlook (yeah, I know, I am probably late to the party) but my calendar is now shared with my other half so she doesn't have to keep asking me where I am when she is planning social events. Absolutely marvelous - does what it says on the tin.
In Outlook 2007, right click on your calendar and choose "Publish to Internet".