Global Browser Statistics
If you are interested in a general breakdown of overall browser usage, there are a number of web sites that provide listings for free. They also offer usage statistics on other useful criteria such as screen resolution and various web technologies.
The Counter (http://www.thecounter.com/stats) bases its global statistics on millions of visitors using thousands of web sites registered with their service. This is an easy (and free) way to get a good general overview of browser usage.
Another useful resource for browser information, as well as for tutorials on a number of web topics, is the W3 Schools site (http://www.w3schools.com/browsers). Their statistics seem skewed toward the development and technically savvy community, as evidenced by the fact that the Firefox browser makes up nearly 20% of all usage, compared with only 8% at the more general http://Counter.com as of this writing (September 2005).