Using Effects - Opening Up Audio's Toy Box
Effects can range from subtle to startling, and everywhere in between. Whether using some EQ to beef up a voice, a compressor to tame a scream, or some reverb and delay to create a comedic moment, once you learn to use these tools, your biggest problem will be wanting to use them too much.
About.com Guide Joe Shambro explains the basics behind using EQ for the human voice.
Kjaerhus Audio offers a set of free, high quality VST effect plug-ins that cover all the basic types of signal processing. These are some of the best free VST plug-ins available on the internet.
A great article from Harmony Central on how compressors work. A compressor on your voice track can yield a full, "bigger than life" radio sound.
When you start out podcasting, a simple tweek on the bass or treble for your voice can be fine, but for those who own mixers or want to use more complex EQ plugins, here's an article from Harmony Central that explains how to take control over all those little knobs.
Free, high quality VST plug-ins from DigitalFishPhones. The pack contains compressor, De-essor, and Expander / Gate effects - all useful for voice overs!