virtual machine choices in Debian

["H.S." <hs.samix@gmail.com>]

Hello,

Many months ago I had first installed a virtual machine, VMWare. I used 
it for a few months and then never touched. IIRC, it was free for 
students back then.

This week I looked it up again (I still have the virtual machines 
installed) and wanted to reinstall the new version of VMWare Desktop. I 
noticed that it is not free anymore but comes with a 30 day trial feature.

So, what free and preferably open source choices do we have for virtual 
machines in Debian? Pros and cons based on your experiences will be 
appreciated.

Thanks.
->HS