Wow, every time Google rolls out a new feature I fall more and more in love with them. This time my adoration is focused on a nifty little tool in Gmail and Google Calendar that allows you to create events and invite people. You can enter all the information in the form and it evens adds a link to Google maps for the address. You can track which guests are coming and who has declined and there is a discussion feature for people to add comments. To make things even better there is a little check box that allows the people you've invited to invite people.
Once you've entered all of your information and email addresses and clicked on send, a nice invitation will pop up in your invitees mailboxes.
This is definitely a feature I will be using in the future.