Johan Stuyts, one of the fine guys at Hippo showed me SAnt ("Shared Ant") build system he's been writing up for Hippo software.
This a thin layer on top of Ant and Ivy, and using Subversion as a repository.
SAnt relies on "project domains", that define organisation-wide or multi-project wide settings and "project-types" that define the layout and build system for particular kinds of modules.
Everything is stored in Subversion, which means that installing the tool and setting up a new project is just an "svn checkout" away.
Compared to the default Maven2 behavior, the developer masters the time when updates of dependencies and tool chain occur (it's just an "svn update"), and compared to Ant, the shared project types allow to centrally define standard project layout and build systems, sharing them between projects if needed by means of svn:external links across subversion repositories.
Needs a bit polishing to reach a wider audience, but definitely interesting!