I've got an MS in computer science, and the thing I've noticed missing the most when I've worked with people without a degree is not their programming/software engineering/etc. ability (they seem to pick that up naturally just by doing), but their theoretical computer science instead. Mind you, a lot of crappy schools don't teach that either, but it's really useful on occasion.

I'd say go through Knuth's The Art of Computer Programming in your spare time, it's got one of the widest coverages of that sort of stuff, and it's actually a lot more approachable and better written than a lot of the other similar textbooks out there. Assume it'll take you a while though.