I want to do some audio recordings of sessions, both for my own purpose and to share.
What do I need? How do I do it? How do I make it listenable to others?
A good omni-directional microphone is a good start, if you can't have a dedicated mic for each person. I've used a Snowball switched to its omnidirectional setting before, and it's good enough for documenting a session with good-enough sound quality that you can hear everything. (For the quality of a good postcast, a single mic won't cut it and you'll want dedicated mics, and might consider a seating arrangement that prioritises recording quality and sound separation. That's beyond my experience, but sounds like it's beyond what you need anyway.)
As for software, I've used Audacity to record and post-process play session audio, for personal documentation and sharing purposes. It's well-suited to the job as it gracefully handles the very large file sizes that you'll get when recording hours of audio. As an editor and post-processing tool it is also quite powerful, and it exports to various compressed formats for fize sizes that are more reasonable for sharing.
To record, one of the best tools I used is Audio Hijack Pro (costs money, but well spent), coupled with a good omnidirectional microphone I inherited from my past as a musician. Alternatively, you can use the same strategy with a (large) iPod touch or iPhone, which can record audio input.
For sharing I strongly suggest a different strategy. Keep notes (either from recorded audio or taken on the spot during the session) and create a private wiki somewhere to write the story down. It is faster to access, and easier to search a specific piece of information. I used this method with great success and people loved it.
In addition, if you are very lucky (like us) you can use a very unique method for keeping the events. We had a fantastic comic artist in the group.
This is my Cleric Elf while pregnant
This is the whole party
This is us, playing
Clearly, not an easy method, but it makes things so beautiful to recall.
You will need a conference microphone (omni-directional) and some way to connect it to your recorder (i.e. computer). Conference recordings will necessarily have some echo that will diminish quality; unless you want to pad your playing area, you can't avoid it.
Making it listenable to others will involve some post-production (filtering and especially cutting; I use Audacity) as well as some instruction to the players beforehand like "only one person talking at a time"; "no talking while eating"; "tell, don't point"; or similar things. All of these will make listening to it much more enjoyable for everyone (including your group!).
That said, I think that most actual play recordings have major problems with keeping it interesting to listen to for outsiders (besides the aforementioned stuff).
It can be beneficial to not include the entire recording but only segments of it and transition by a voice-over which you record during the editing process. This way, you leave out the boring, long-stretching parts and focus on what is important. You can mark important points for cutting in the recording by whistling or clapping your hand thrice, this will show up nicely in the editing software.
I think Story Shtick is a good example of a well-made recording.
Think about your goals and needs. If it is primarily a personal recording and tool, audio quality isn't important and you could record directly on a laptop or something (Audacity is great for Windows; if you have a Mac you are all set out of the box). If your goal is listenability, better quality cardioid or omnidirectional mics are a good investment. We recorded digitally to a low-end M-Audio recorder and the quality was always good.
If you want to share, consider why and edit appropriately and ruthlessly. Games take a long time, and much of that is not compelling audio. Editing can be very time consuming if you want it to sound crisp and professional.
Consider excerpts with commentary, for example. When I was podcasting, we omitted actual play entirely, focusing on the setup and then a debriefing about what went well, what went poorly, thoughts on the system, etc.
At the low end: a good quality omni mike in the center of the play area, and preferably a cloth on the table and additional felt in the die-rolling area to reduce dice noise.
At the higher end, good quality individual lavalier or headset mics, a small mixer, and a sound tech to run it, and a multi-track digital recording sound card... which said, you should be pushing $5,000 for the hardware alone... and accoustimass on the walls, silent chairs, no paper on the table.... and no dice, either.
In the midling range, a good multi-channel input sound card (last I looked, about $300 or so), and two or three good directional mics, each feeding a channel... if you have enough channels and drive space, one mic per player is ideal.
In any case, after recording, you need suitable editing gear, be it hardware or software based editing. And you need software for final output formats.
I had a quiet player who loved gaming but wasn't always the most dynamic character in the group. She did, however, enjoy taking notes (and thus being the one who spotted my lame puns and the subtle subplots and links to past events). I still have bloody great ring folders of all her note-taking that we dip into now and again for a nostalgic trip.
My point is that some of this 'side responsibility' is a great way to involve the milder, more refined players at your table. If someone tends to follow the loud guys and only get animated when specifically called to use their skills, ask them to help out by jotting down notes or even using the technological suggestions given above to record the session (letting them hit pause every time high dice rolling combat or a conversation about last night's Dr. Who is a godsend).