In the past, we've used the iAtkos distro for this, but iAtkos hasn't updated for Mountain Lion yet, so I used the 'OS X 10.8 Mountain Lion bootable DVD for Intel PCs', by Olarila. I won't go into details, but you can download these copies from about any bittorrent website by using a bittorrent client (it's about 4.5 GB in size). Instead, you'll have to rely on pirated 'bootable DVD' copies of Mountain Lion, also known as 'distros'.

Virtualbox : This virtualization suite is free, and though it doesn't offer official support for Mac OS X, it works well enough.