I'm interested in Computational Chemistry/Molecular Modelling with a view to drug design. I don't have anything like the resources available to the big pharma companies, but as it turns out, that doesn't matter in a hobbyist setting. Think of it as a manual equivalent of running the DrugDiscovery@Home or the old Screensaver lifesaver project ( http://www.chem.ox.ac.uk/curecancer.html )
All the software you would need can be freely obtained as you aren't doing this commercially, although I try to use as much of my own code as possible, being the geek that I am. There's nothing to prevent people modelling proteins, docking molecules into those proteins, making toxicity predictions, and so on, with open source software and a moderately good PC.
Sure, I'll never be able to run in vitro screening, and I'll definitely never get to the stage of running a clinical trial, but I'm going to have fun at the beginning of the process. If I found myself without a job and with a spare $5-$10 million, then I'd love to take it to the next stage!