Step1: Setup 3D Acceleration
1a Select your Virtual Machine and Click Setting
1b Click on Display, then set your Video Memory to 12b MB, and then enable 2d and 3d acceleration
Step 2: Installing Guest Additions
2a Start and let the Virtual Box boot up
2b Click on Devices and select Install guest Additions
3a Goto System > Preferences > Appearence > Visual Effects
3c Click on Extras and install and configure Compiz the way you want it.
Done. Now you can run 3d acceleration running Ubuntu in VirtualBox. My favorite effect... Water. This will allow you to do the Cube and most 3D effect. The last clip is my to-the-point video on the subject.