wedding paper divas .. awesome. you cant buy the paper and print them yourself cheaper..
We actually designed and printed our own. Bought the paper and had fun as a couple putting them together. Not sure it's what you want to hear, but if you're on a budget, it's a great way to go!
thegreenkangaroo.com or tgkdesigns.com
we chose the layout and stuffed them ourselves. it was really easy to "do it yourself" the paper quality was beautiful and you can ask for samples on the ink and paper as well. they arrived on time, no complaints. loved them! i even used their designs for our wedding website. just copy and paste!
We designed our own and got them printed through Vistaprint! They were cute, creative, good quality, and really affordable (go to retailmenot.com or couponcabin.com for some discount codes). If you want to save yourself even more money, have people reply via your wedding website (on theknot) or via phone (for those who aren't internet-savvy) -- this way, you save money on return postage, and your outgoing envelope will be cheaper because you won't have to worry about an extra envelope in there! It takes some extra time in setting up the website response, but once it's up and running, it's TOTALLY worth it!! :)
Click on each tool to see a sample.