I don't have time today to write a thorough HowTo today, but if anyone needs help, I'll be more than happy to write one up in the next few days.
I've been able to use OpenSolaris, Haiku, Linux Mint Cinnamon, Ubermix, Ubuntu, Win2008R2 (with PRTG and radius), XP PRo, OSX Mountain Lion, and OSX Maverick within my GNS3 topologies. Just PM me, or ask in thread, and I'll be more than happy to help out with the setup to get those to work for you.
And just a heads up, but the Frame Relay Switch Icon is pretty wonky, if you use more than one (and even then, I couldn't get it to work right). I'm going to attempt to get the Cisco 1000V virtual switch working in either VMWare or Hyper-V next.
I also use Jeremy Cioara's CBT Nuggets course, as they are awesome, but I also use the labs at GNS3Vault (free to register, and he has tons of labs for GNS3).
If you are interested in NX-OS, Dave Lammle has made his NX-OS simulator freely available. I've also got the eNSP sim from Hauwei, but I haven't used it yet, so I can't verify if it's worth a dang or not.