Last year we saved a lot of money making our own wedding invitations for our daughters wedding.
We purchased the actual invitations at Wal-Mart. They come with the blank invitations, reply cards and all the envelopes in a kit.
They also tell you how to print the invitations right from your computer.
To dress them up, I purchased the green velum paper, (you could use co-ordinating velum to match your wedding theme). Then we made the jackets to cover the invitations, just by wrapping the velum around the invitation so that it met in the middle and creased it firmly. Then we folded back the corners, and punched 4 holes ( 2 on each side) at the middle of the velum and tied swiss dot ribbon in a bow on each side. I also added a daisy ( to match the border of the card) in the center of the invitation, so that it peeked through just above the jacket.
To enhance the envelopes I purchased a stamp and ink pad in the co-ordinating sage green to stamp initials onto the envelopes. I used an embossing powder to sprinkle over the ink, and with a heat gun ( used with embossing powder)I heated the powder, and it gave a nice shine to the letters. If we had ordered the invitations from a company, the price quote was $500. but by making them, It only cost under $100. Quite a savings.