Some time around 2005, Slashdot ran an article about a new hosting company, MacMiniColo that was taking advantage of the new machines that Apple had just released to offer cheap hosting. I got in contact with them, and a little while later, I had a Mac Mini, sitting in a rack somewhere, running OpenBSD and acting as my dedicated server. A 1.42GHz G4 CPU, 512MB of RAM, and an 80GB disk was (and still is) more than adequate for my needs. The biggest load on it is eJabberd, and even that only used under 1% of the CPU.
I had really great service from these people. The hard drive failed a little under a year after I bought the Mini, and Apple refused to honour the warranty because they couldn't find the records of the sale (then, a few weeks later, they could, but by then it was out of the warranty period). MacMiniColo replaced the disk for me at their own expense.
After five years with them, however, I had a little look around and noticed that VPS hosting has gone down in price a lot. I've written a book on Xen, so I thought I might try a Xen-based VPS now that FreeBSD has Xen support.
GigaTux only claims to offer Linux, but I dropped them an email and they were happy to install FreeBSD for me. I still haven't tried the Xen-enabled kernel yet; they installed the stock x86-64 kernel in an HVM domain for me and performance has been fantastic.
I'm sharing a server with 64 other guests and in spite of that performance tends to be better than my ageing Mac Mini. I was getting 1000IOPS while untaring the ports tree, which is far more than the Mini's old 2.5" laptop drive could handle, and is amazing considering that it's going via the slow, QEMU-derived, emulated device, rather than the fast PV driver. I've been installing software from ports, so everything is compiled on the machine, and even that has been fast.
And my Mini? They found someone else who wants it, and offered me about a third of what I paid for it originally - not bad depreciation after five years of constant use. Shipping it back to the UK would have cost almost as much as buying one on eBay, so I sold it on. Hopefully someone else will get some good use out of it.
As an aside, I've been really impressed by how well OpenBSD works on Mac/PowerPC hardware. If you've got an old Mac Mini lying around, chuck OpenBSD on it and you've got a reasonable low-volume server. The newer ones, of course, are x86 hardware, so will run just about anything.