Image from here. The quality is much better in the actual invitation.
Granted, this isn't the same as getting an actual item in the mail, but it is cheaper, greener and a much needed improvement over the current online invitation platforms. The service isn't free, but it is really, really cheap. Invitations are managed by buying books of stamps, just like at the post office. You can purchase 40 stamps (for 40 invitations) for only $5, or 150 stamps for $10. You get 25 free stamps by signing up here, and they never expire.
The possibilities are really endless. This service could be used for anything from baby announcements to save-the-dates to dinner party invitations. Also, they offer logo integration, which will allow businesses to announce openings, introduce new team members and even invite customers to special events.
I recently used the service to send New Year's greeting cards, but I wouldn't hesitate a minute to use the service for a party. It includes invitation tracking and an automatic RSVP function. There are endless options to choose from when designing your invitation or announcement. I definitely recommend browsing around the site and using the 25 free stamps to send out an announcement or invitation of some sort, even if it's just having friends over for wine.