Broadly, there are two options for including remote participants while recording a podcast:
Live recordings mean that all of the participants are recorded live as a single track. Participants may talk to each other with some combination of VoIP, mobile, and good ol' fashioned landline phone calls.
Skype the most popular example of this, and (not surprisingly) the most popular VoIP option for podcasters. It supports high-quality Skype-to-Skype calls via desktop, mobile, and web apps, and phone-quality calls with anybody else with a phone number.
(🔥 = most popular choices)
VoIP calls can be recorded using software or hardware.
The main differentiator for these services is that you can use very-high bitrates — high enough that remote participants can sound like they're in the same room.
Source-Connect Now — While in beta, Source-Connect Now is free. When out of beta, pricing will start at $8/month, with a middle tier plan at $24/month.
ipDTL — ipDTL starts at $30/month for web-only calls at 72 kbits/sec, up to $70/month for plans that support for “HQ” audio, video and the ability to call landline/mobile phones.
Some VoIP solutions also help automate “multi-enders” — a workflow where high-quality call recording is done on each participant’s side as well and then merged after.
(🔥 = most popular choices)
There are 3 ways to record VoIP calls, one of which is Skype-specific:
My recommendation is to avoid option #1, especially on Windows where Skype is undergoing a transition from a traditional “Win32” app to a “Universal Windows Platform” app.
When recording with a computer there are two kinds of options: Skype plug-ins and OS-level recorders.
OS-level recorders have a couple advantages: (1) They work with more than just Skype, and (2) they eliminate the possibility of a version mismatch between Skype and the plug-in.
Ecamm Call Recorder for Skype (Mac, $30) — This Skype plug-in can record your own microphone input and the output of your Skype call as separate tracks in a single QuickTime movie. An included utility allows you to split that file into separate files for each track, and convert them to other formats.
Amolto ($30, free for audio-only) — A Skype call recorder that supports audio and video.
CallGraph (free!) — An easy-to-use, audio-only Skype call recorder.
Evaer ($20, trial available) — A Skype call recorder that supports audio and video.
MP3 Skype Recorder (free!) — Only records to compressed MP3 files, which will result in lower quality recordings compared to alternatives which can record to uncompressed WAV or AIFF files. Try to avoid, but if you must use be sure to set "Recording BitRate" to 128.
Pamela Call Recorder (15€) — Paid version supports unlimited recording, can record up to 15 minutes for free. Note: Pamela has a mixed reputation reliability, and is listed here mostly for completeness’ sake.
Audio Hijack (Mac, $49, records for 10 minutes without a serial number) — It does Skype recording and a lot more, and as such it’s a crucial tool for many podcasters. Rogue Amoeba is a great developer and has been making great, award-winning audio software for the Mac since 2002.
Piezo ($19) — Record audio from any application, or from audio inputs like microphones. Records from Skype and other VoIP apps, and can save the audio to distinct channels for easy editing.
Soundflower (Mac, free!) — This open source software allows apps to send audio to other apps. (A pre-built installer is available at the top of the description.) For example, you can use Soundflower to send Skype output to apps like QuickTime Player, Audacity, etc. for recording.
Total Recorder SE ($18) — Record VoIP (Voice over IP) calls or Internet-telephony conversations when using programs like Skype, Google Talk, Yahoo voice, MSN, etc. Both parties can be recorded in a VoIP conversation. For more information, see their tutorial: Recording VoIP Calls and Internet-telephony Conversations.
SnagIt ($50) — Capture audio and video. (Can’t record VoIP participants to separate channels. TechSmith blog post: “How to Record Skype, Google Hangouts, and Webinars”)
A “mix-minus” setup allows you to record Skype calls.