Here are some interesting new approaches to using your Mac
F-Script Anywhere allows you to embed a scripting environment into any currently running Cocoa application. It also includes an object browser letting you take a really close look into your favorite programs.
The Application Enhancers framework and the various applications built on top of it also patch themselves into other programs. Insane tools for unsane people.
Spring is a next generation desktop for OS X. It is based on what they call
concept-centric computing rather than the traditional document- and application-based approach. In any case it is visually quite impressive.
SubEthaEdit (formerly known as Hydra) is a distributed, collaborative text editor. Using Rendezvous you can share your document with other users on the network (or the Internet) and edit it together: everyone has his own cursor and typing is in real-time. It also makes for a slick standalone editor.
is a graphical tool which anyone can use to build programs by plugging parts (like PerlPad snippets)
It is written in Perl (using the GTK libraries for its GUI),
and looks somewhat similar to
Automator, but was developed independently.
If you like Java, but you also like scripting languages, you should take a look at
BeanShell, a lightweight (and easily embeddable) scripting language with Java-compatible syntax.