I have been listening to podcasts for about 3 years now. The first podcast I have ever listened to was This Week In Tech and I have been hooked ever since. Podcasts are a great way to learn something while on the go. Here is a list of stuff I listen to

This Week In Tech
This is a weekly podcast about the tech news for the week. The best episodes are the ones with John C. Dvorak in my opnion

.NETRocks
This is a show with episodes on Tuesday and Thursday, mostly about .NET but also some Open Source and JavaScript now and then. Shows with Ted Neward and Chris Sells are my favorites

Security Now
This is all about security, Steve Gibson is the host and he usually dives deep inside a topic. Take for example the multi show crypto one
Security Now 30: Crypto Issues
Security Now 31: Crypto 102
Security Now 33: Symmetric Block Ciphers
Security Now 34: Public Key Cryptography
Security Now 35: Cryptographic Hashes
Security Now 37: Primes and Certificates

Diggnation
Diggnation is hosted by Digg founder Kevin Rose and Alex Albrecht. The purpose of this podcastis to discuss some of the top stories from Digg.
This is great to listen to on the treadmill since it is not a serious show

Windows Weekly
A weekly show with Paul Thurrott of the Super Site for Windows. Paul Thurrott isn't a Microsoft fanboy and doesn't hold back, if he thinks a Microsoft product sucks he will let you know.

Herding Code
A weekly podcast hosted by Scott Allen (OdeToCode),Kevin Dente, Scott Koon (Lazycoder)and Jon Galloway. The focus of this podcast is mostly develoing with the Microsoft stack

SQL Down Under
A podcast about SQL Server hosted by Greg Low, SQL Server Experts are the guests

This Week In Science
TWIS is a 1 hour weekly science/technology radio news show broadcast on KDVS 90.3 FM on Tuesdays 8:30-9:30AM PST. Is hosted by Kirsten Sanford and Justin Jackson

The Disciplined Investor
Hosted by Andrew Horowitz and all about investing and the markets, very interesting show and always good guests. Check out show 64 with John Perkins, author of Confessions of an Economic Hit Man and The Secret History of the American Empire

FLOSS Weekly
A show all about Free Libre Open Source Software (FLOSS). Join hosts Randal Schwartz and Leo Laporte every Saturday as they talk with the most interesting and important people in the Open Source and Free Software community. If you want to know what is coming up take a look here: http://spreadsheets.google.com/pub?key=pYAJMbVobYCTro_z4LGo3ZQ

There are some more podcasts I listen to but these are my main ones.

If you have any good ones that I should know about please leave me a comment