I have recently discovered Weddingmapper.com. I think it has quite a few great features on it. In addition to being able to create interactive maps for your website or to print maps for your invites. You can updload your guest list to it and track your RSVP's electronically. It let's you keep track of what each person wants for dinner too. There is a page that lets you create a seating chart. There is also a page on the site that helps you keep track of thank you cards that you have sent or need to send..
I started using it last night. I am so glad I found it. I think it is going to be really helpful. Thought I would share...