http://www.javaranch.com/journal/200603/AntPart1.html is a good article about some advanced techniques.

Visualizing Data: Self-Documenting Ant files is a good page to start this brand new page with.

I like the idea of having a help task like this:

Figure 7. Help Target Output: After you instrument the code with a "help" target, launching Ant with no arguments gives you the same result as using the "-projecthelp" argument.

If made the default task, it will really run ant -p -f so kind of self-documenting.