At Test Often Joe Ponczak lists seven metrics that you can use to make your methods more testable, "Seven Metrics to Improve Your Unit Testing". Experienced unit testers will probably be familiar with the metrics but it never hurts to review. I mainly mention this because it is the blog for CODIGN Software which makes some nice reasonably priced Eclipse plug-ins for writing JUnit tests and analyzing code coverage.
p.s. I sure don't like the white on black color scheme on the blog though.