Invitations

We used US Postal Service regular mailing, nothing special, and the invitations got to our guests pretty quickly. We dropped them at the post office on a Saturday and many of our guests received their invitation on Monday.

We used USPS for those we didn't normally see in person (those were just handed to them in person). The longest it took for someone to get the invite was about 1 week, and that was for a friend who lives 1/2-way across the country. Assuming your invitations are in an envelope, UPS will end up being way more expensive than USPS.