Burd's Proxy Searcher is a free tool which can find public proxy servers, test them for performance and to make sure they work in your area, and then configure various browsers to work with them (IE, Chrome, Firefox, Opera) with a click.
Getting started can be as easy as launching the program, and clicking "Search". It then begins querying Google for public proxies, filtering out anything you don't need (transparent proxies maybe), testing whatever is left, and displaying details of anything which passes: the IP address, port, country, type (Anonymous, Transparent etc), and speed. Searches may be run in parallel to improve performance.
If you spot something which looks interesting, click the browser icon to its right and Burd's Proxy Searcher will configure the program for you. (You'll need to configure other programs manually.)
And if you'd like more control, or just a better understanding of how Burd's Proxy Searcher works, clicking Tools > Settings will reveal some interesting configuration options.
Just one example: click "HTTP (Google)" and you'll see the search keywords used by the program to find proxies; http proxy list 3128. If you're unhappy with the quality of the search results, or you have more specific needs, then entering your own keywords here might help.
Version 4.7 adds German language support.