I just built a stand myself, you can see in the thread below. I found it easier to design it from the outside in. But build from the inside out.
I don't have any design software so I ended up drawing everything on graph paper. When it comes down to it you can have all the fancy drawing and computer print outs you want but when you’re building it everything comes out a little different unless you’re a professional. I'd lose a 1/16" or 1/32" here and there even when using some pretty fancy framing tools. After 4 or 5 layers of material and cuts it can come out to 1/8" which can make your carefully computerized images wrong.
If you just want a general idea about how to make a cabinet I can say a little bit about what I did. First thing I did was decide on the shape and size of the top so I could fit the tank I knew I wanted, ended up with 3/4" pine laminate. 24x13x16 tank. Extra length front to back was used to accommodate plumbing. Wrap was 3/8" which is easy to find and is more or less a decent standard to work with since it is thick enough to provide a decent amount of rigidity and won't make your tank weigh 1000 lbs. I used 2x2 for framing instead of 2x4 because my small tank and I wanted my stand to accommodate a drawer. I reinforced with steel brackets.
I have a bunch of tools router, table saw, chop saw, biscuit joiner, finishing nailer and stuff so I could go as buck wild as I wanted. Cabinet doors are tough though (if you want it to look pretty), drawer wasn't a cake walk. If you just make a framed box and wrapped it, making a stand is easy. Just make sure everything is square and Level.
One note if you make for an acrylic tank you have to support the entire bottom not just the edges or your going to have a few spilled gallons on your floor.
If you have the time the tools and the patience it can work out well. If you want some specifics make a little drawing about what you want done, I’m sure there are some pretty accomplished carpenters here that could help you figure out the specifics.
~Pork