We (I) decided to do them ourselves because there was a specific vision to how they would be. So I ordered heavy cardstock in greens and blues, designed an invitation insert on GIMP and had it printed over at overnightprints.com in the form of a postcard with rounded corners.
Next I got a stamp that I loved (and had used in the card design) and some embossing ink (which makes stamped images rise up off the paper once you emboss them with a heat tool), stamped green glittery trees on little squares of light green, folded dark green around the cards that I glued in place (actually T did that part), and tied those bad boys up with a ribbon (I did that part - he's not so great with the bow-tying, but that's okay. That particular thing can be a wife's job in every situation where it would arise, I think).
These are the 2nd reception invitations, the wedding ones were mostly the same, but in blues and with a different insert (one that felt a tad more formal).
And that was that! I think they ended up with the right combination of formality and fun - not too dressy, not too casual, the same way that I hope the events will be.
I can't believe there are only a couple of weeks left. What an amazing time.