Is there a way to evaluate OS X without purchasing Macintosh hardware?
Solution 1:
You can't run Mac OS X on non-Apple hardware. It's not allowed by the EULA for OS X and it is technologically enforced by having key parts of the OS in the copyrighted hardware ROM installed in the Apple hardware. Furthermore, all versions of OS X prior to Leopard and non-server versions of Leopard and Snow Leopard had architectural issues that prevented virtualization even if you wanted to hack something like VirtualBox or VMware to virtualize them in violation of the EULA and copyrights.
Incidentally, while you can virtualize OS X Leopard and Snow Leopard Server as well as both versions of OS X Lion, the license still limits this to Apple Hardware.
VirtualBox supports virtualizing OS X Snow Leopard Server. You can find instructions for doing this here. VMware Fusion supports virtualizing OS X Leopard and Snow Leopard Server as well as OS X Lion client and server versions.
Solution 2:
If you live near an Apple Store, you can always take an afternoon or evening to "evaluate OS X" and the machines in the store. The employees seem to be very gracious and happy to let you evaluate for quite a while.
What do you want to "Evaluate"? Whether it runs the programs you need it to run? Whether it runs quickly? How long the battery lasts? How much they weigh?
Also - you can speak with the sales team - I've never had any problem returning a Mac that I bought to an Apple store and getting a refund if it's not what I needed. When there is uncertainty of the fit of the product, I've long had them say they will waive a restocking fee and I believe there is no return fee chain wide at present.
Solution 3:
The OP is asking for a "supported" way and I guess that means "Apple approved", but I still want to point out that it is very possible and actually quite easy to run OSX on commodity hardware. There's a whole community out there dedicated to making it as easy as possible. My workstation (Intel core i7, Nvidia graphics) has been running the latest version of OSX for two years now, with no problems.
The installation procedure that once was more of a hack is now down to booting from a USB stick and installing from an original (bought) OSX DVD.
The relevant term to put into Google is "OSx86".
Solution 4:
You can get a refurbished Mac starting at $599 for a Mac Mini. You can usually find even lower prices for older Macs on eBay or Craigslist.
Solution 5:
Obviously this is already marked as answered, but you can always hire a Mac or find a very cheap second hand one to buy.
... For example I have an old 15" MacBookPro that I'd hire out for $20 a day plus deposit, I'm in Sydney, Australia though so that's probably not a great deal of use to you.
But try a want ad on the bulletin board at CWRU, or wherever works best in your locality.