First of all I have to give props up to Rhonda here at WBC! She is amazing and created our invit...
My FH and I are using "wedsite.com" to have people RSVP. This website is so very cool, and it's inexpensive. For 6 months it was only $29!
I really love this website for a number of reasons! It's password protected, it allows you to upload as many photos as you want, you can upload MP3 songs to play in the background, it's an interactive website with a virtual "book", it allows you to tell your story, and give info on your wedding and reception, along with maps! And it's so much easier and better for the earth and the physical space at my already over-wedding-cluttered home than having mail-in invitations! I don't have to worry about losing people's RSVP's, or having the postal service lose them for me. I think people will be more likely to do the on-line RSVP because it's quick and convenient and it can't get lost like a little RSVP mail-in card could.
You can also buy a CD copy of your wedsite for when the wedding is over!
For those of you who want to check it out, the address is