Someone asked about a company to use for invitations, so here's an idea...
I do PR for a non-profit and we're always looking for ways to save $$. For smaller events (of the 200-500 guests range), I've used Paper Direct
http://www.paperdirect.com. If you use the "jumbo postcards" (the size of half a sheet of paper), they can make nice invitations. You just feed them through your printer, and voila! They're set up 2 per sheet, with a perforation. They come in a box of (I think) 50 sheets which yields 100 invites at about $25 per box (cheaper if you order multiple boxes). If you go this route, you can either mail them with a label on back...OR to make it nicer, put them in an envelope. (When I've done this, I put directions on the back or sponsor information!) Also, another $$ saving tip for this route...buy envelopes at your office supply store, they're much cheaper than the ones in the catalog!
(Edited for spelling mistakes & typos!)