I've been thinking about a "digital chemistry set" for a while. It's something that would certainly be fun to play with and that we have all the information to do--chemical reactions follow established rules and exceptions could be hardcoded in.

I've thought about an organic chemistry chemical program. If you're not familiar, a huge component of organic chemistry consists of memorizing and understanding reactions and their mechanisms, and reactivity of organic molecules. A digital lab where you could mix arbitrary compounds together and see what happens could be a powerful educational tool suitable for supplemental use with another ochem course/self study.