Download VMWare Server from
http://www.vmware.com/products/server/
Extract the tar file to somewhere convenient, in this case I'm going to extract it to the desktop.
Execute vmware-install.pl which is in the vmware-server-distrib folder that you just extracted. You will be prompted by questions about install directories. I managed to get away with pushing enter for the default value on all of these questions. It may need to recompile some files if it isn't familiar with your kernel version. This isn't normally a problem if you have a c/c++ compiler.
If you don't have a c++ compile (
here's how to check and install one) then get one from synaptic packaged manager.
When asked, make sure you respond "yes" and give your ubuntu username when prompted to change the username (if this bit goes wrong then once VMWare Server is installed you will need to uninstall it and start over). After answering more prompts the installer will ask for your serial number. This can be obtained from the VMWare website for free.
Caveats:
1) If you accidentaly left the username blank then you will need to run the following command to uninstall the vmware server. You will then need to start the install again.
sudo /usr/bin/vmware-uninstall.pl
2) To access the server admin you need to visit either https://127.0.0.1:8333/ui/ or http://127.0.0.1:8222/ui/ in a browser. You can then login with your ubuntu account username and password.
Ubuntu 9.04 VMWare Server