You're already using Podcasts to help you get prepped for the ASWB exam. (You're not? Start here.) There's plenty more free exam prep disguised as other types of info all around the web. A great example: all the social work/psych webinars just waiting to fill your brain with the very stuff that may show up on ASWB test questions.
DorleeM over at Social Work Career Development has been kind enough to gather bunches of potentially helpful webinars, month by month. Don't worry that the dates on many have passed--search for archives or upcoming events.
A word of caution: Focus your listening on social work fundamentals rather than cutting edge--possibly more alluring--topics. Given a choice of CBT vs. EMDR, say, know that it's CBT that's going to show up again and again on the exam.
Find something especially useful, come back and let us all know via comments. Happy hunting!