We don't provide binary nightly builds at the moment, but if you want to build Ant from sources, you can use a Subversion snapshot.
Ant and Ivy are using Continous Integrations systems to improve the development process. Note that these are no official builds and they are not endorsed or even supported by the Ant team. But if you have problems with testing the latest (successful) build, you are welcome to post that on the developer mailinglist. You can directly access the builds of Ant and Ivy on these CI installations:
The Apache Software Foundation hosts an installation of the Hudson CI-system which Ant + Ivy use.
JetBrains is offering Ant the service of a Continuous Build on their TeamCity system.