VMWare came to me through Ubuntu. It has a client version preloaded. Though I've used the server version for Windows quite extensively running a virtual 5 server LAN for 3 months. I also have used Microsoft's Virtual PC running a server an client for a couple of months. VMWare is very good and easy to manage, Virtual PC is okay for servers and pretty good for clients, but only if they're Windows. You can run some linux distros in VPC but not officially, and you can't run it on linux.
When I first started using VMWare through Ubuntu, I registered with them and all that good stuff and after a month got an offer from them to try the server software for free, which I ignored and then like a month they sent me a link to to the full version for free. I didn't ask for it, they just did it. I hope they do it again. If not, I can get it from school.
