The basic structural plans will come with the oven. Beyond the box shape that you must have to support the oven unit, the sky's the limit for design. fornobravo.com has a ton of pics to give you some ideas. The ovens come in either kits or fully intact and ready to go, depending on what you are looking for.
Mugnaini and Forno Bravo (the US licensee/distributor of a big Italian brand) seem to be the most popular. I've never heard anything but great things about both. And my personal experience with both backs that up.
As a few here can attest, my Forno Bravo, which is the unit pictured in the link above, works very well. I used it as a burn-down pit for a pig roast earlier this year and had it way too hot, even for Neapolitan pies (probably 1100F plus). It was none the worse for wear after many hours. But usually, I can keep it within a very good range around 800, which works for me.
PS, looking at the fornobravo site, I now see that it has a (somewhat grainy) pic of the JeffB oven and hog pit.
http://www.fornobravo.com/pizza_oven_photos/residential_ovens/Chicago10.html