Do you already have a computer with a sound card that can act as your digital recorder? You just need to add some inexpensive recording equipment and software to your PC, and you can produce high-quality, effective voice recordings easily. What other gear do you need?

Microphone
To get your voice into the computer, you need a microphone. Don't use the crummy little one that came with your computer. High-quality, inexpensive mics abound and sound far better than that trash. For basic voice work, I'd suggest a large diaphragm studio condenser such as those made by MXL, Audio-Technica, Shure, Rode and others. There are several choices around $100 with some terrific mics in the $300-$500 range, too.

Microphone preamp
Microphones put out such a low amount of electricity that their signal needs to be boosted. The sound card's mic input includes the necessary preamplifier. Unfortunately, much like the cheapo mic that shipped with your box, most sound card mic preamps are too noisy for serious work. In a pinch you could use it, but at least, use it with a better mic.

For the preamp, you can choose either a small mixer to work with your mic or a dedicated audio interface. Mixers essentially let you connect several microphones and other devices (such as a CD player) to one place and adjust their volumes independently. Behringer and Mackie make some decent little mixers. Alternately, two good choices for stand-alone preamps include the DBX Mini-Pre Tube Mic Pre-amp and the ART Tube MP Studio V3 Mic Pre-amp. Both are under $125.

Many professional dedicated audio interfaces (some USB-based others Firewire-based) include decent preamps and a far better soundcard. Options here include Edirol UA-25, M-Audio FW-410, or the Focusrite Saffire.

USB
Another prudent choice is a USB-based mic, such as the Samson CO1u or Blue Snowball which plugs directly into your USB port and appears as a soundcard to your recording software. This means you don't need to invest in a mixer, preamp, or better soundcard as they have all this built-in. You'll still need your built-in soundcard for audio playback, though.

Speakers and headphones
While computer speakers are adequate for recording, editing, and finishing basic recordings, those built-in to laptops are useless. Invest in some decent powered speakers, such as the M-Audio DX-4 for this purpose. Wear closed-ear headphones that keep sound leaking from them from being picked up by the mic.

Recording software
Choose recording software with editing facilities for fixing mistakes, compiling the best bits, adding music and/or sound effects, creating special effects, and delivering your finished voice tracks in the formats you need. I like Sony Sound Forge Studio 8.0 for the PC, but Audacity is a freeware alternative for Macs, Windows, and Linux.

Quiet recording space
Your goal is to record a clear, intimate voice track, and that means keeping noise and the sound of the room OUT of the finished recording. Professionals record in a sound booth specially designed to keep noises out and make their voice sound good. These costs thousands of dollars and are a bit impractical for occasional work. A clothing-filled, walk-in closet works as a makeshift sound booth, though.