Google Guice is a really great Dependency Injection Framework and worth a look. Especially the performance and – much more important – the configuration using Java code in a very intuitive form are great features.

They have now released another project that can be very, very helpful. It is called Google Collections and provides some small but helpful classes.

A series describing the details can be found here:
http://publicobject.com/2007/09/coding-in-small-with-google-collections_08.html