Recently BoingBoing filled its readers in on how to tap a phone line. It's not too hard! All you need are a lineman's handset, some recording equipment, and a free stretch of time to spend in jail. But incarceration isn't necessary if you're a real (amateur) investigative reporter; there are plenty of legal and semi-legal ways to gather info. After the jump, a complete guide to everything you need to set yourself up as a DIY spy. Only to be used for a righteous cause: Recording Phone Calls Federal law allows recording of phone calls with the consent of one party on the call, meaning you can legally record any phone calls you're a part of. State laws vary, however: in some states you must have the consent of both parties (not New York, though). See here for a full guide.

You can record phone calls on normal handsets with a cheap recorder hookup, like this one from Radio Shack. You can also record calls onto your PC, either with an adapter, or, more simply, by using Skype. There are also services that will record your cell phone calls for you, and allow you to access them when you want.
Other Recording

A simple little digital recorder is a great device that can be slipped into a pocket or left in a corner and record ambient conversations for hours. For long-distance audio recording, you'll need something more powerful, like a parabolic microphone that can amplify sounds 300 yards away. Works great for hearing bird calls; if you're using it to listen in on people, you may be a creep.

For visuals, there are plenty of discreet, handheld digital camcorders that should meet most video recording needs. To secretly record what's happening in a room, you can buy camcorders that are hidden in everything from plants to smoke alarms. Again-if you are using these to be a creep, you will and should be locked up.
Researching People

Google! It's a wonderful tool. Nexis People search is a quick and efficient way to categorize your searching by what the person does, where they're from, their company name, etc. Paid search services like Intellius can take small bits of information about people and search for public records and contact info for a nominal fee. Names can be parlayed into phone numbers and email addresses, and vice versa. Public records from these and other similar sources are broader than you think. Recent Nexis upgrades, for example, can give you everything from a person's cell phone number to info on their gun licenses. You never know what you might find. The Freedom of Information Act is designed to give you access to government records that don't have a good reason to be private. This is largely political; under the current administration, lots of stupid things are private. Obama should be more open (one would think). Get your FBI file, why don't you? Better yet, get someone else's! A government guide to FOIA is here, and a citizen's guide to the process is here. Also legal: searching through someone's trash, if it has been placed out for disposal in a public area. Although this may get your ass kicked. Tracking Movement

A small GPS device like this placed in someone's car can help you track them for days. If you're not in law enforcement, this is probably illegal, so never do it. Modern cell phones have built-in GPS devices, which would theoretically make them a great way to track the movement of individuals. But that's generally impossible without the assistance of the carrier, unless the person is using an opt-in tracker and posting their movements themselves on Dodgeball or something. So this one requires great hacking skills or a mole at the phone company, and is illegal besides. A useful overview to cell phone tracking is here. For observation purposes, digital binoculars combine a camera, video recorder, and binoculars in one product. Final Thoughts Are you spying for a righteous cause? If not, give the world some privacy, why don't you? Either way, you might consider learning Krav Maga or carrying a Taser. Those being spied upon tend to object.