I just registered for a community seder at Ahavat Olam, a synagogue here in Vancouver, and noticed a neat feature on the registration form: a mechanism for inviting friends to register with you. Powered by GiftTool, the form asks for the names and e-mail addresses of any friends you'd like to invite along, and offers a text area for adding a personal message. Later in the registration process, you're even given the opportunity to request seating near these (or other) friends.
This is a terrifically easy and smart way to boost attendance at any community event. Since most people feel more comfortable attending events with friends, making it easy for them to invite their friends along encourages attendance and helps spread the word at the same time. I'll be sure to include an "invite a friend" feature in any future event registration forms -- and would be curious to hear about other services that make this as easy as GiftTool.