At Dnr TV there are two episodes with JP Boodhoo, where he gives an introduction to test driven development:
- Test Driven Development with JP Boodhoo, Part 1
- Test Driven Development with JP Boodhoo, Part 2
If you want to see unit testing and TDD used together with a whole bunch of other agile practices, I would recommend watching the sceencast series Autumn of Agile. This series shows the development of a fully unit tested application from start to finish.
As for podcasts, check out the following:
- Polymorphic Podcast – Jason Bock on Unit Testing, Code Coverage & Analysis
- Hanselminutes – Scott Hanselman on Test Driven Development
- Hanselminutes – The Last Word on TDD, with Scott Bellware
- Software Engineering Radio – Gerard Meszaros on XUnit Test Patterns
Since mock objects are a quite important part of unit testing, these podcast episodes might be of interest as well:
- Hanselminutes – Scott Hanselman on Mock Objects
- Dot Net Rocks – Eli Lopian on TypeMock.Net
- Dot Net Rocks – Oren Eini on RhinoMocks
- Dot Net Rocks – Oren Eini on RhinoMocks 3.5