[agersant]

This may be a simple oversight and I hope I don't sound too pedantic but you may need to broaden your definition of developer a bit. Developers who work on OS, games, embarked systems or professional applications (think CAD) are not very likely to need these anytime soon. More knowledge is always good so I'll check some out anyway!

[erkkie]

You're right, I should've narrowed the scope to client-server or perhaps "the web" (although the exact lines are blurry).

[clone1018]

Vagrant can help developers who make OS and Games :). It can be used for simple testing on another OSes and environments.