It seems that ant dependency management isn\'t great to say the least... But, is there hope? Today there are better choices for build or project management such as maven, iv
I've been using Ivy for the last 4 years (way before it joined Apache) and haven't had any regret.
Without knowing much about your Ant files, it's a little bit difficult to give a definitive answer but I guess that the projects are build in one go. This means that they can't individually publish their artifacts (or jar files) into a central repository.
The solution is to use both a central (for common libraries) and local (for your project) repositories. You can take a look at my public projects and especially the ivysettings.xml file because they use exactly this very principle.
Just to disillusion you: dependency management in combination with a build system is hard! Unless you have a really simple example, this is not a no-brainer, and you will have to invest some work.
If you want to or have to use Ant, Ivy is definitely a good choice. Being an official sub-project of Ant, it integrates relatively smoothly.
Here's my take: use the best of both worlds: Maven just for dependencies and Ant for your day-to-day build heavy-lifting:
Why you should use the Maven Ant Tasks instead of Maven or Ivy
There's a new open source build system for Java called EBuild (features) that is a great alternative to Ant/Ivy as it is especially good at dependency management.
There's some detailed articles on the deficiencies of Ant and also Maven on the site.
If you already use Ant, then your best bet is to use Ivy for dependency management.
http://ant.apache.org/ivy/
It provides a rich set of ant tasks for dependency manipulation.