In the spring of 2006 I took a course at the Harvard Extension School, CSCI E-124, Algorithms and Data Structures, which was fascinating but frustrating. I think the material in this course is absolutely essential if it is your goal to work on interesting problems with smart people. If you are thinking of taking this course, I hope I can offer you some advice here that will improve your chances of success.
My principal frustration was that although the course's teaching staff is extremely strong in analytical skills and presents the material clearly, they reward you most for your analytical skills and reports you write and offer nothing in the way of support when it comes to programming. For example, you may hear more than once, "I haven't programmed in years, I can't help you with questions about your code." The programming assignments got me bogged down in infrastructure so much that I spent considerably more time building tools than I did running experiments or writing reports.
Immediately after the course was over I got a random email from the ACM offering me a chance to read technical books online through the members' portal to Safari Enterprise Library. After a little browsing under Computer Science, I stumbled on Mastering Algorithms with C by Kyle Loudon, August 1999, ISBN 1-56592-453-3 (O'Reilly). Normally I skip books offering algorithms in C as very 1980s, but I tell you, I took one look at this book and wished I had read it cover to cover before taking E-124. I don't know how much of the code the teaching staff would let you use—you'll have to ask them—but I probably could have used much of it directly and then been able to focus more on experiments, analysis and reports. The instructors care about your skill as a scientist.
Another thing I noticed, on the analytical homeworks vs. programming assignments: if you write a correct answer in a short paragraph or two you will get full credit for the question, but if you write several pages of text developing an argument, including diagrams, and then your answer is either wrong or not quite right, you will get almost no credit, or less than you expected. In other words, you won't see "Nice try!", you'll just see a low score for not being right. So, figure out what the right answer is, then figure out a short way to express it.
If you can take this course all by itself and do nothing else, do! Disconnect the phone! Go into hiding. Then you should be fine. Unless, of course, you are on campus. Then find like-minded students and form discussion groups. Start your homeworks and problem sets the minute you get them. You will need every scrap of time to finish them.