Open-source libraries abound. Thousands of projects thrive and (mostly) languish at Apache, SourceForge, CodeHaus and right here at java.net. Project directories like FreshMeat, Java-Source and CodeZoo try to make the chaos look less irregular.

But above all the rest, there are projects that have changed the field, some of them declining, and some strong as ever. Here are my top three:

1. JUnit
2. Tomcat
3. Struts

So, what is your top three^*?

* Try to choose objectively (I know that even your plumber has wrote a new web framework, but it doesn't mean that it's that good). Entries with more than three names will be subject to removal :(