There are a few podcasts devoted to Doctor Who out there. I like PodShock--it's mainly 3 guys discussing the show, but they also have different people who submit their own segments (Big Finish reviews, convention reports, etc).

There's another one called WhoCast, but I haven't heard any of these yet.

Also, they're not calling it a "podcast", the way Sci-Fi does for Ron Moore's BSG commentaries, but there's a commentary track for "The Christmas Invasion" available on the official BBC site.

PodShock is a pretty good podcast. For those who use iTunes or have iPods, theres a version with chapter markers and different segment graphics, options that are very rarely used. It's useful for jumping over spoilery descriptions and other segments.

I also heard the commentary track, and had a very hard time keeping it in sync. My guess is that there was an additional edit or two made after the track was recorded, which caused things to be out of whack.

Whomix radio is all about remixes of the title theme, available either as a podcast or downloads from the main site. There are hundreds of them, going back years, though earlier years are only available via Bit Torrent.

Here's a remixed opening theme and credits for Doctor Who.

http://youtube.com/watch?v=UqO6xecXfqg

There's confirmation from the BBC now, that all of S2 will be accompanied by online podcasts ala BSG.

The commentary that goes with "New Earth" is quite interesting and should be heard after watching the episode and possibly the Doctor Who Confidential "New New Doctor". As the commentators are David Tennant, Russell T. Davies and Phil Collinson, you get the interesting mix of someone who was on set, someone who wrote the episode and someone who was behind the scenes arranging everything. They seemed to get along quite well, with no one really dominating the conversation. David Tennant is pretty good about asking the random questions/random tidbits that fanboys and fangirls might want to know.

I haven't heard the series one commentary yet, so I can't really compare and contrast.

http://cultmovies.libsyn.com/index.php?post_id=81109

Here's an episode of the awesome Cult Movies Podcast dealing with Doctor Who, although discussion of the show actually doesn't come up until halfway through since they somehow get sidetracked into all kinds of hilarious discussion about the Harlem Globetrotters.

My favorite bit: "I remember before one season they did an interview bragging about how much bigger their budget was this time, and then they opened the season with the Doctor fighting a giant chicken."

You know, I can't remember any story, let alone a season opener, that involved poultry in any context. Which story are they talking about?

It's not specified beyond being a Seventh Doctor story.