Every so often, I will get something that is mass-emailed to hundreds of people that I'm sure I can provide a very deep and useful answer to. Today's challenge is a Mac-compatible voice recorder that can record phone calls, but be flexible enough to handle recording interviews that will later be the basis for print work AND apparently for possible release as a podcast. Yikes! That is a very flexible recorder! Therefore, my options were fairly narrowed-down. Here was my response:

You mean physically connects to the phone? Is it important to do it on an actual handset?

For example, I would use Skype and eCamm Call Recorder. I use these applications for recording my own podcasts, and I have never looked back. There are also solutions that will let you plug straight into GarageBand if that's your editing program.

This is exactly the setup I used to record this interview:
Blogging Fringe Interview with Poofy Du Vey (Courtney Cunningham)

Using Skype to call another Skype account is free, and making calls to land-line phones or cell phones is handled via a flat-rate, and international calls are just a few pennies per minute.

If you use skype, you can buy any USB headset with a microphone (I recommend the ones that use USB over other solutions, because you're using a Mac).

Plantronics Foldable USB Stereo Headset
This headset even comes with a separate (replacable) USB audio device - this is the most flexible, so you can use the headphones as normal headphones or through the USB audio port.

Olympus TP-7 Telephone Recording Device
For recording from a physical phone instead of over VOIP, this product seemed to get a lot of good reviews on Amazon. I've never used on myself.

I think the basic Idea is that you put this in your ear and then hold the phone up to that ear - it's just a small microphone that plugs in to whatever recorder.

Griffin iTalk Pro - Microphone
An extremely simple option if you have an iPod is a voice recording accessory built for iPods, like a Griffin. Most of these have an input jack for an external microphone in them, on top of a mono or stereo mic. Just make sure they are compatible with your version of iPod - 3g, 4g, 5g, Nano, Touch, etc.

Edirol R-09HR High-Resolution WAVE/MP3 Recorder
If you want to go for the big guns, something like an Edirol is made for super-professional recordings, has built in microphones, accepts line-in and a whole bunch of great features - and it records to SD or SDHC cards - completely Mac-compatible. You'll see a lot of folks recording to a Marantz, but unless you need phantom power, that's just too much.

Hope this helps. If not, I'd be happy to have a deeper discussion.

If you're looking for more podcasting help, I MUST recommend the BlogOrlando unconference coming up next weekend. Saturday, Sept 27th at Rollins College. FREE. There will be some really amazing speakers and discussions there.

Edit: For my own setup I use an M-Audio MobilePre USB and two MXL V57M mics, along with a couple of On Stage stands, shock mounts and XLR cables.