One of the things I miss about college is learning all number of things, hearing about ideas I'm unfamiliar with, and gaining new interests. My love of Gregorian Chant can be directly attributed to the Music Appreciation class I had to take, and one of the first steps I took towards leaving Christianity was taken in my Bible as Literature class. I've thought about taking some college classes at either the local community college or at UCSD or SDSU just to have something to do, but my work schedule makes it a bit difficult. I may still do it (my local community college has some evening and weekend classes which would work with my schedule), but for now I'm stuck scrounging for knowledge on the Internet. Fortunately, there's a lot of it out there.
I believe it was MIT who blazed the trail with their Open CourseWare. They have some good stuff there, but it's somewhat hit or miss if you're looking to be able too listen to or watch entire lectures. Nowadays other universities have also followed suit by putting some of their courses online. Yale's selection is much more limited than MIT's, but they make up for it with high quality video recordings of all the lectures as well as some of the course materials. What's better, the video recordings can be viewed on my iPod Touch without reconversion (on that note: does anyone want to buy a used iPod Touch? I bought one in September and received a second as a gift this Christmas). I've been watching Introduction to the Old Testament, and it's good stuff. Berkeley has podcasts of classes that are being taught this semester and appear to have a good selection. The audio quality can be a bit iffy, but I suppose I can't complain too loudly since it's free. There's a whole list of universities that have open course content at the OpenCourseWare Consortium
In addition to actually free content, there's also content that's practically free but not legally so. The Teaching Company has lecture series from various college courses that they sell, but much of this content is on the Internet. Their stuff's good too (I can't recommend highly enough any of the courses taught by Dr. Bart Ehrman), but their editing makes the lectures a bit cheesy and artificial. But content-wise, it's top-notch stuff.