Christian Pekeler has written a great tutorial for using AspectJ with WebObjects. I mentioned AspectJ here on Jan 10, 2001, but never did get the chance to play with it like I hoped. Christian has really armed me with what I need to know to get up to speed with it, and I'm grateful for it. :-)

Stepwise: Aspect-Oriented Programming with WebObjects

Christian is also a project admin for the WOUnitTest project on SourceForge.