Ant´s own resource page lists a lot of links, books and articles. Here are some more.
Books
IBM Rational® ClearCase®, Ant, and CruiseControl: The Java™ Developer's Guide to Accelerating and Automating the Build Process by Kevin A. Lee published by IBM Press -http://www.ibmpressbooks.com/title/0321356993
Java Development with Ant by ErikHatcher, SteveLoughran published by Manning Publications -http://www.manning.com/hatcher/index.html
Ant: The Definitive Guide by Jesse E. Tilly and Eric M. Burke published by O'Reilly - http://www.oreilly.com/catalog/anttdg/
Apache Ant - The Buildmeister's Guide - Second Edition by Kevin A. Lee published by Lulu Press - http://www.lulu.com/content/1022721
Java Tools for Extreme Programming: Mastering Open Source Tools, Including Ant, JUnit, and Cactus by Richard Hightower, Nicholas Lesiecki ( ErikHatcher contributed to Ant sections ) published by John Wiley & Sons, Inc. - http://www.wiley.com/cda/product/0,,047120708X,00.html
Ant. Das Java Build-Tool in der Praxis von Bernd Matzke, Addison-Wesley, http://www.addison-wesley.de/main/main.asp?page=deutsch/bookdetails&productid=13459&SID={18BA3C59-985F-4E1B-8463-4A60D29D2EED}&TOKEN={2EA05B80-7976-432C-B8A5-4520CDFB1113}
Ant: The Java Build Tool in Practice by Bernd Matzke, Charles River, http://www.charlesriver.com/titles/ant.html
Java-Entwicklung mit Ant (ErikHatcher, SteveLoughran translated into Deutsch) http://www.mitp.de/vmi/mitp/detail/pWert/1409/titel/Java-Entwicklung%20mit%20Ant
Documentation
Appendix E of Java Development with Ant is included in the Ant 1.5.1 distribution
Ant 1.5.1 Core Task Examples Quick Reference: http://www.discursive.com/articles/2003/01/ant_core_ref.html
Broken Link!
Presentations
Ant and JUnit Junit and how to run it from Ant
Ant1.7 Presentation based on Early Ant1.7; some things may be incorrect
Testing Why those tests matter
Other
Ant Resources - Articles, Books, FAQs, Forums, Presentations, Tutorials, Wiki.
Ant Forum - Browse or search Ant mailing list posts archived by Nabble. Users can also create sub forums to expand discussion.
Comment déboguer un script Ant - by Vincent Brabant -[fr], How to debug a build.xml file with Netbeans?
Ant Specialist Search - provided through Google co-op functionality. (homepage gadget coming soon)