I personally use Adobe Soundbooth for my editing. As with all Adobe products it is expensive, has a steep learning curve but is high quality. If it didn't come in a package with other software that I purchased I wouldn't spend the money on it since I am only a hobbyist.

Raven Lite is a free software from the Cornell Lab of Ornithology that will let you edit your recordings. I have heard decent reviews about it but haven't used it.
http://www.birds.cornell.edu/brp/raven/RavenOverview.html

If you have other suggestions please leave a message so that others can know about it.

Update - As of April 2020 I've starting using Audacity. The learning curve was much easier than Adobe Soundbooth and works as well for my needs.