I write virtually all of my code using TestDrivenDevelopment and UnitTesting. I believe strongly in AcceptanceTesting, but have had limited success in getting organizations to buy-in. (Instead, they seem to fall back on manual testing by a bunch of QA people.)
[http://idiacomputing.com/moin/PrimaryKeyGeneration#head-d7949da7a424b68c0ae6279e11b7e8718331321e DbUnit and autonumbered primary keys]
Some other things that look interesting:
[http://patterntesting.sourceforge.net/whatis.html Pattern Testing] allows you to check coding/design standards across the project. This looks very interesting, but I haven't tried it. (thanks to Jeff Waltzer)
[http://www.jdemo.de/ JDemo Framework] mentioned by Ilja Preuss on TestFirstUserInterfaces@yahoogroups.com
[http://developer.spikesource.com/wiki/index.php/Projects:TestGen4WebDocs TestGen4WebDocs] is a FireFox plugin for recording web interaction to be played back later as a test. It reportedly works with [http://ftp.mozilla.org/pub/mozilla.org/firefox/releases/1.5b2/ Firefox 1.5 Beta 2] but not Firefox 1.0.7 or Firefox 1.5 RC 1.
Agile Security Testing of Web-Based Systems via HTTPUnit [http://agile2005.org/RP4.pdf PDF] describes, among other things, how to bypass HTML form field length limitations.