I've been running versions of Windows and Linux on VMWare for ages, but I've never tried any virtual appliances that would run straight off from VMPlayer. I was poking around the VMWare site I came across JanusVM (http://www.vmware.com/vmtn/appliances/directory/392), which looks quite interesting.

Are these appliances actually useful, and do you know any "cool" ones that'd be good to have a look at?

Hmm, what that does do? Some kind virtual machine where you can run several OS in same time in one machine? Bad website, hard to find simple information what it is what it does what are key features, they should hire someone to rework that site.

Have not used those, but perhaps would be useful at some point, I have played a bit with Microsoft version of virtual machine.

I have terminal server kind of thing running in my Linux, very handy and faster than Microsoft solution with lighter hardware. FreeNX is what I use for that, can connect from other windows or linux machine and do almost what ever can be done locally, still learning more from these.

Yes, VMWare make virtualisation solutions, there are some free ones (server, client) available here http://www.vmware.com/products/free_virtualization.html. They also do enterprise scale solns with ESX server and stuff. They support all the popular OSs you'd want to run, Windowses, Linuxes, Solaris etc.

What used to happen is that you make your virtual machine yourself, but you needed the OS and licenses for that. Now, with VMPlayer one can download premade solutions and simply open the relevant vmdk file in the player for it to run. That's what I think it does anyway..

VMWare Server and Player will now let you make your own machines, or you can create VMs from a variety of sources (physical computer, Virtual PC image, Ghost image) using the Converter program. The VA (virtual appliances) are pre-built and configured machines.

I've tried out a couple of linux distributions, had a play with the sourceforge-in-a-box VA and mySQL. It depends what you're interested in playing with as to what's cool.

I installed server, but I don't think I need it - I'll be trying out Player instead in the near future.