I've been using the Eclipse editor (www.Eclipse.org) for about 2 years now, and I really like the latest version of Eclipse which is 3.3. If you will be using Eclipse with Drupal, which is to say with PHP, you can save yourself a lot of time and trouble by installing the "all in one" version of Eclipse for PHP (http://www.eclipse.org/pdt/). Don't forget, you want the all in one PDT (Php Development Tools).

When using Eclipse to edit Drpal modules I found that I had to change a few preferences to let Eclipse know that .module files were in fact PHP files. I would detail what I did, but I followed the instructions on a post on the Drupal site, so I'll just refer you to that. http://drupal.org/node/75242