How do you convince coworkers/stakeholders to try new technologies? [closed]

Question

I've got a coworker/manager/stakeholder who is very conservative when it comes to adopting new technologies. I completely understand why: we have a lot of internal expertise with Java, MySQL/Postgres, and so on, they're well-established, and there's lots of good support for them.

But technology evolves, and sometimes newer technologies are better suited to today's tasks. It makes sense, for example, to do heavy numeric processing in something like Python+Numpy. Some kinds of simple web sites are faster and easier to implement in Ruby/Rails. Processing hundreds of gigabytes of logs a day is well suited to a Hadoop M-R architecture.

But I often encounter a lot of resistance to bringing new technologies into the mix, even when I think there's a strong case for it. The resistance even goes down to minor details, like using a heavy JavaScript front-end and web services rather than server-side heavy JSP for a recent project. The most common objection is that because we don't have significant expertise in the technology, it won't be maintainable if I'm not available to do it myself.

How do you work with people like this to overcome these kinds of objections?