Wow, I almost feel like if a program has run for 50 years, it should be allowed to keep running out of sheer respect :-) But I know what you mean.
I think one way to get Ruby into organizations that are skeptical about it is JRuby, which can blend nicely into the Java scenery. I'm not advocating subterfuge -- nor need it be done that way, since the claim would be that JRuby is just something that runs in the JVM, and indeed it does. I don't know whether that's relevant for your situation, though.
Another strategy is to work on a small, intra-organizational scale -- meaning, write some Ruby stuff that's flying under the radar, and find people who you think might be enthusiastic about using Ruby in ways that don't require permission, aren't public-facing, etc. It's hard to predict but at some point if Ruby develops a track-record of usage, and there's anyone in a decision-making position who's willing to look at what it's done, something could start to shift.
Ruby training coming up in September! David A. Black and Erik Kastner team up for fast-paced, four-day Ruby intro, in New Jersey, September 14-17. See http://rubyurl.com/vmzN or contact David.
Perhaps you could start with build scripts. Buildr has become a pretty solid replacement for its Java-based counterparts. Build scripts would also be a safe sandbox to experiment with the language and see how people feel about it.