Speakerphone: If you don't want to spend any money, this is probably the cheapest possible way you can record phone calls. Use a speakerphone and set a tape recorder or your PC's microphone right next to it. It works and you might get some good quality recordings out of it. But as you know, speakerphones are annoying to the people you call and you have to take turns talking, as opposed to being able to talk at the same time with any other method. Instead of using a speakerphone, you should at least spend $5.49 on a suction cup microphone...

Induction Coil Mic: This method of recording is nice because it's portable and can be quickly hooked up to almost any telephone, even a pay phone. You don't have to have access to the wiring of the phone, you just stick the suction cup on the back of your phone's handset and plug the other end into a tape recorder, stereo or your computer. If you have a phone handset that has electronics in the handset (i.e. the dialing keypad is IN the handset) then you might end up with interference in your recording. It's best to use the suction cup on a phone where the handset is separate from the rest of the phone. But if you don't have a choice, try positioning the suction cup in different places, like on the side of the handset or on the top. You can even stick it on the opposite side, where your ear normally goes, as long as you can still hear the conversation okay. If you do this, you'll probably need to wrap some tape around the suction cup and phone to hold it on. You can buy the suction cup phone recorder at Radio Shack for $5.49. The part number is 44-533.

In-line Recorders: This device has always been my favorite method of recording phone calls and has almost always produced the best quality recordings. An in-line recorder plugs into any phone jack in your house and will record phone calls from any phone on that same line. These are great for tapping lines - you could hide one of these in a closet with a tape recorder and nobody would ever know that their phone calls were being recorded. If your tape recorder has a "remote" jack on it, this device will automatically start your tape recorder each time a phone in the house is picked up. Then it will stop recording when the caller hangs up. Radio Shack carries 2 different models and I've never been able to understand what the difference is between them. I own both of them and they both appear to do the exact same thing even though one is more expensive than the other. The expensive model is $27.49 and claims to be "smart." The part number is 43-2208. The cheaper model is $24.19 and it's part number is 43-228. Go with the cheap one.

In-line Phone Cassette Recorder: This device works just like a regular in-line recorder but it has the added convenience of having a tape recorder built into it. You can either hook it directly into the phone line so it will record every phone in the house, or you can hook it to your phone's handset so that it only records from your phone. It can be activated by voice or it can just start rolling tape whenever a phone is picked up. I had a problem with the voice activation, though, because the first word would always be half cut off. It wasn't quite sensitive enough. These can also be picked up at Radio Shack for $79.99. The part number is 43-473.

Police Scanner & Cordless Phone: If you happen to own an older cordless phone (900 MHz or 10 channel or 25 channel), you might be able to record phone calls directly from your police scanner. Simply figure out the frequency that your phone is on by scanning the 900 MHz range while you're on a call. You can also get the frequencies for the 10 & 25 channel cordless phones on this page. One you've got your conversations playing through your scanner, you can hook the earphone outputs directly to your tape recorder or computer. Or you can just set your scanner next to the tape recorder or the computer's microphone and hope for the best. If you own a 2.4 GHz phone don't even bother trying.

Modems & Software: If you have a voice-capable modem in your computer, you might be able to record phone calls directly from the phone line that's hooked to your computer. One program I know of that does this is Call Corder. I've never tried recording phone calls like this so I'm not sure how well it works. There's lots of other software packages for doing this but I'm not going to list them all since I don't know much about any of them.