While podcast support is pretty good on desktop Zune, the dependence of Windows Phone 7 on synching with this software means most people will only have one chance per day to download their favourite podcast.
Podcast! is a new free app by Melting Bot software, that allows one to easily find and stream podcasts over the air, something not possible with the built-in Zune client.
The service however lacks the ability to download podcasts, making unfortunately only half a solution, but hopefully that will come in a future update.
The software can be downloaded from marketplace here.