So at long last my fav OS X tool is back. Applejack is a wicked utility that does all the command line work when in Single User Mode under OS X. Applejack has been updated to be 10.6 compatible.
Get it now at Macupdate.com

I have a new favourite tool that I used to have to buy. VirtualBox.
It’s a software virtualizer for installing guest OS’s inside of. I used to use Parallels Workstation for this but needed to upgrade it with my last OS upgrade but didn’t have the coin. Virtualbox is free from SUN Microsystems.
Find it through:
Macupdate.com