i dont know of any software to build a canopy and stand. they arent really that hard to build.....just stop buy your LFS and check out other stands and canopies. you should have a good idea on how to build them.
yeah they are out there. Actually you tell it what the height you want. tank dimensions etc and it tells you how many 2x4s etc you need at what length. Im not sure what the site is just do a search.