Most of us use evite for invitations. But there are some interesting alternatives which you may want to check out for your planning your next party.
Check them out.
1) http://www.socializr.com/ : Started by Friendster co-founder. a brief description can be found here
2) http://www.skobee.com/: A brief description can be found here
3) http://renkoo.com : A brief description is here
4) http://www.mypunchbowl.com/ : a brief description is here