Chematica was covered here before, awesome software, I which I had excess to it 
I would love to play around with Chematica myself, if only I had the chance, but, these huge pieces of proprietary software that charge like $10,000 a license (or something like that) aren't always that much more sophisticated than what open source projects can do (with the right amount of dedication and contribution, at least).
It's like Wolfram / Mathematica / etc... Sure, super useful software if you can afford it (or can get a license by some other means), but totally replicable.
The awesome thing about computer science is that the investments are virtually non-existent. I've only recently gotten into chemistry and it's already costing me a small fortune (glassware, precursors, solvents, and the especially fancy shit like Soxhlet extractors, etc).