Archive.org is fantastic for text - I've used it extensively in my research. Unfortunately podcasts don't archive so well :( I've been trying to get this podcast: https://web.archive.org/web/20091210030233/http://bitwiremedia.com/wordcast/wordcast-special-edition-live-may-12th-at-6pm-eastern/ but having no luck. I've been in touch with one of the publishers of the podcast and he doesn't have it any more.

Here's a good one that I did find via archive.org though: https://web.archive.org/web/20080427183149/http://www.revolutionizeyourblog.com/askthanks.php