yeh that link elegantweddinginvites is a good one. I did mine complete diy sourcing card stock myself online and designing it from scratch myself too. I wanted high end embossed but just went with designer papers with a felt 3d kinda look, hard to explain. another useful link for designing invitations, we got the fonts for our invite from here, http://www.fontsaddict.com/font/clicker-script.html (<thats the exact font we used for the outside too)
I got mine at www.dreamdayinvitations.com.au where they allow you to customise the look of the invitation in terms of typeface, photograph and invitation wording, names and addresses and all that jazz all on the online system before ordering. It's quite cool actually. Check them out.