Here are some tips to use Ubuntu 11.04 Natty Narwhal on VMware.
First upgrade the host vmware (player) to the latest (3.1.4) version. Although the release notes mention nothing on Natty, the vmware-tools from this version compiles ok on the Natty kernel.
You may have some luck with the open-vm-tools. I didn't had much. It didn't recognized the machine as a VM, but still worked. I was having problems with the video looking very ugly and was thinking it was a vmware-tools problem, but looks like not. Below is a workaround to run on the terminal which makes things beautiful again: