I know we have 7 months to go, but I found this website where we can get invitations super inexpensive, and they were having a free shipping deal for the weekend (not that they wouldn't do it again, but why not now if I can).
150 invitations (you have to order in batches of 25, and 125 was cutting it close to the number we need to send out - lots of singles unfortunately) with envelopes and response cards for just over $80. They're not super fancy, not pocket folds or anything like that, but they have some cute invites if you aren't too set on the fancy invitation details.
www.123print.com