This is a great site for DIY cages, I basically followed his 4x2 instructions when building my own cage out of plywood. You need a router if you want the door to be flush with the rest of the cage, but luckily my buddy has one.
http://www.arbreptiles.com/cages/cages.shtml
DIY cages are cheap, but are a pain when it comes to gluing, sealing, and finishing the enclosure. Also, wood cages can be VERY heavy. I have a couple homemade melamine racks that work great, but are the biggest pain in the butt to move.
I just ordered a boaphile cage because I like the fact that you can get two 4x2's and connect them later if you add an extendable side. This feature should make moving them much easier. It's not here yet, so I can't say for sure how well it will work, but they are very light, affordable, and look easy to clean.
Sentec cages are another great one. They are a little more expensive than boaphiles, visions, and animal plastics, but look fantastic. I will more than likely purchase a couple 8-footers in the future, as well as a CB-70 rack.
I personally don't like sliding glass fronts. They're not the easiest thing to clean, and unless they have a lock I wouldn't trust them with a big snake. Also, it's much easier to pull a big snake out of an enclosure when you can open the whole front, rather than just half of it.