For simulation work, I want to use multiple, independent random number
generators. Does anyone know up to date implementations?

I found randomr but that is inactive sinds 2001 and clearly marked
alpha (http://rubyvm.sourceforge.net/subprojects/randomr/)
I also found some projects from MoonWolf from 2004 but his site
(www.moonwolf.com, see e.g. http://raa.ruby-lang.org/project/random-mt19937/)
is offline. Which makes it hard to get to the code.
There is a generator that uses certain sites, but that is not really
an option.
I am now going to look at the isaac gem, but its version number 0.0.2
does not make me feel very happy.

Did anyone find better implemenations of PRNGs?