I got a B. S. in Computer Science long ago and haven't worked as a programmer since the '80s. If I'm considering trying to get back into programming in a few years, what should I do/study to prepare myself?

There's been a lot of bifurcation IMO since the 80s. Programming was easy when it was all command line, one program at a time. So now it's not just the language, it's the entire ecosystem you have to step into. So choose wisely. The basics are the same, but the frameworks are so much bigger than they used to be. If you plan to do apps, there are a ton of tutorials available from the manufacturers, who obviously want you in their sandbox, not someone else's. If you plan to do PC or Mac, be prepared for a whole suite of tools and libraries. I think the web is the most straightforward place to program. Not like java, but like the scripted languages. As said, find a project you like. Play with it. Take a look at some online courses (http://lynda.com is great for those). Figure out what kind of programming you want to do, on what platform, and then move forward.

3 things come to mind. 1st A lot of now-popular languages were not around in the '80's, so you will want to be sure you know the basics of something like Python and JavaScript at least.  I'm sure others would have different opinions on which specific languages would be good to learn (depends on the problem and your/the market's preferences), but if you learned Pascal and C back in the day, well, you need to get up to speed on one or more of the newer languages. 2nd, the way we program has changed yet again since the '80's.  Structured programming has given way to object-orientation.  You need to wrap your head around classes and objects as implemented in the new language you're learning.  If you don't have a lot of experience working with classes and objects, your background can trip you up working on modern projects that assume this orientation until you come to understand it well enough to code that way. 3rd, a lot of stuff now comes pre-written, either in the language itself, or via open-source 3rd-party libraries.  I'm constantly tripping over getting way too far along in coding something, only to find there's already code out there that can be used.  The job of the modern programmer is often to know what all the good libraries and APIs are and write glue code to build things, rather than to hand-code stuff like sorts, heaps, and other higher-level functions yet again. I can't praise Coursera's "An Introduction to Interactive Programming in Python" enough!  Teaches Python programming using various games.  The course is very carefully constructed and clear.  Rice University, which teaches the course now also has two follow-up courses in the series, after which you would be pretty fluent in Python.  Don't yet have a good recommendation for other languages, tho everything I've ever tried from http://Lynda.com has been excellent.

Given your education and work history, I am wondering why you aren't into going to graduate school and teach at the University level or other options where you can combine your programming skills with your teaching skills? Why lower yourself to just coding given your experience?