I really like how Gradle has solved this problem. You check in the Gradle wrapper (http://www.gradle.org/docs/current/userguide/gradle_wrapper....) into your source control (it's only 56K), and it automatically fetches Gradle for you if you don't have it. Updating the project's Gradle version is just a matter of changing one or two lines.

It's cool to think that the only requirement for anybody to jump into a Gradle project is to have the JDK installed. "git clone <project>", "./gradlew assemble" is all it takes for you to fetch all your dependencies and build the project.

I think it'd be interesting to see if Vagrant could incorporate something like this; it sounds like it would help your use case.