Marijuana Radio was started with the the the legalization movement in mind, but has since then grown into much more. Now the "potcast" (har de har), covers a wide range of topics. The hosts Paul, Mckenna, Dank, are cool characters and have even cooler guests.
Weed Watch caries two shows, S.A.F.E.R. abd John Doe Radio (JDR). The two shows cover informative and entertaining topics. From Interviewing high level marijuana activists, to playing indie musicians. Weed Watch is a THC Media project. They're also behind Stoner Forums, which is an awesome contribution to the community. So check them out.