I haven't seen one for dreamhost specifically, but I have seen people mention that it works. I'd check out the php dreamhost tutorial, and look at the tutorial on the xcache website.
I have put all of the php cache plugins into production (mmcache, phpa, eaccelerator, xcache, etc), and xcache was the only one I didn't have trouble with at some point. It works very well. It would be worth trying to install, even if no dreamhost-specific instructions exist.
I'll put up instructions as soon as I have time to do implement it myself.
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