VMware server has been added to Canonical’s commercial software repository. In order to try it out, add the commercial repostiory through Add/Remove Programs and search for VMware. Or insert
deb http://archive.canonical.com/ubuntu feisty-commercial main
into your /etc/apt/sources.list. The package name is vmware-server. You’ll need to install
sudo apt-get install app-install-data-commercial
sudo apt-get install vmware-server
And it will install VMware server for you. If it does not work for you, try Qemu.