If you haven't heard of Paperless Post it's a fabulous website that offers beautiful & sophisticated notes, holiday cards and invitations. Sort of like evites....but classier :)
I've used it for dinner parties and acquaintances holiday cards. It lets you manages guest lists and create an address book. The Junior League uses it for all their meetings invites and reminders; it's just a little cuter than a casual e-mail.
The spectacular Kate Spade has combined forces with Paperless (just in time for the holidays) for a gorgeous collection of note cards, thank you's, holiday cards and invites!
My Favorites below: