(1) I wish I had time to build self-education software. This is a wish carried over from my brother, who came up with the idea; a system which hands you exactly the practice problem you need at the moment, to challenge you, keep your interest, but not give you something you can't do. Ideally, the problem sets would be created and shared in a wiki-lije online community (which is the main difference from current high-end education software!) The broadness enabled by this could revolutionise education, job training, and certification. (Since the program estimates your skill level to determine what problem to give you, sitting potential employees down for a session on the machine would give valuable information about their abilities.)
(2) I would also like to have the time to build a powerful "open work" software in the spirit of mechanical turk, love machine, rentacoder, and others. The hope would be to emphasise love machine's social aspect, but mechanical turk's "all are welcome" aspect. Ideally, the environment would also feel like stack overflow-- you can build reputation by answering questions for free, so that you are more likely to get paid in the future. There are a lot of issues to be dealt with here! The nature of contracts, the details of any "reputation" system... it's complicated. However, it would be great for the efficiency of the intellectual labour market!
(3) I want to build a Bayesian reasoning system capable of acting as mankind's store of knowledge, so that all arguments for and against certain points can be kept track of and weighed properly against the evidence. This is the least realistic of the three dreams, but if it could replace/augment Wikipedia, it would help to end debates like global warming (or, rather, force the debate to proceed entirely from empirical evidence and in a logically correct manner). There are lots of big problems with this one, including the problem of verifying sources of empirical data.