Mini-Server
This is so odd I just had to post it: macminicolo.net
Yes, that's right: a co-location host specializing in Mac minis, the smaller-than-a-shoebox low-end desktop-in-a-box device introduced by Apple in 2005. For $35 a month plus startup costs, you too can serve your company website from a small, unassuming white box.
I think that OS X server has a lot to recommend it, although for web services I still think you have better bang for the buck with commodity Linux machines (although opinions vary). But when people talk about OS X Server, they are usually doing so in the context of its preferred hardware platform: Apple's Xserve.
Not exactly an Xserve, is it? Speaking of which, here is what their FAQ has to say about Xserve hosting:
Do you take XServes?
We recently stopped taking XServes as the new Intel XServes required an incredible boost in power. Also, nearly all potential XServe customers found that they could work on a Mac mini just as well, saving them money.
No particular surprise there, I suppose… many Windows hosts could get by with quite a bit less horsepower than they actually pay for as well. A load test comparing the mini to a Dual G5 Xserve provides the numbers; while the Mini comes up short of the Xserve, it isn't by much.
Price/performance may not quite Pencil out against the larger Apple servers, (if you need an Apple server for some reason) but if you are interested in sizing your expenditure to your expected load, I suppose the Mini provides an option you might not otherwise enjoy. The real argument against them is the lack of robust design… notebook hard drives, lack of redundancy. But the new mantra is lots of cheap, capable hardware instead of a single monster rig. You can still get commodity hardware of comparable performance cheaper than the mini, but nothing that will run OS X out of the box so easily. I'll be waiting over here for the first massively parallel Mac mini server cluster to be announced.