After trying and failing to get my hands on a temporary Mac to develop an iPhone app for a client, I\'ve started to look into VMware Workstation to virtualize OS X. I was w
Prepare for an onslaught of replies on the EULA.
Technically your best resource would be the OSx86 website which is here http://wiki.osx86project.org/.
And their page on virtualisation is here http://wiki.osx86project.org/wiki/index.php/Virtualization
Importantly though, developing for the Mac and iPhone are very similar, and if you are serious about doing good developmenet for your clients you should probably invest in a mac mini at the least, which is less than $500US more than just buying the OS by itself.