I’ve only really explored Maven. I was hoping that I’d get a chance to look at Ant and some of the Ruby inspired build tools, but msbuild looks like the only tool I’ll need to be exploring for a little while - my new job is quite .NET focussed. Anyway this Blog post does a great job at listing the pro’s and con’s of Ant, Maven and Gant. Gant is a Groovy powered build system which the Grails guys are using.
Updated: Oops forgot the link!