John Ferguson Smart's Blog: JavaOne 2008 - FindBugs is a great little tool, and it just keeps getting better!
There are a lot of static analysis tools out there, but Findbugs is unique. Where Checkstyle will raise 500 issues, and PMD 100, FindBugs will only raise 10 - but you damn well better look at them carefully!
That is a slight over-simplification, but it does reflect the philosophy of FindBugs. FingBugs uses more sophisticated analysis techniques than tools like PMD and Checkstyle, working at the bytecode level rather than with the source code, and is more focused on finding the most high priority and potentially dangerous issues.