Website Promotion

By May of this year I will have a website that will provide services and resources to minorities in America. By the end of the year I'd like to have close to half a million members.

My question for any of you creative folks, especially those who have help to manage and promote a website or messageboard, is this.

What are some creative (and legal) ideas you've used/seen/heard of to get people to a website?

One of my ideas is to give a prize to the individual who sends out the most new invites in a given month. A gift like an I-Pod or PS2 or 30 CD's of your choice or whatever.

Now when I say new invite I mean an e-mail address that:

1) Is not currently an address registered with my site

or

2) Has not previously been sent an invite.

If you can't think of any ideas, then what would you like to have the chance to win as a gift?