In the new Ubuntu 9.04 Jaunty Jackalope, Intel graphic (video) drivers 965 (x3000 or x3100) are blacklisted so you cannot run Compiz thus your desktop effects cannot be enabled. There is a way to enable desktop effects, though this is not recommended because

Today we soldier on to Desktop Effects with Compiz Fusion. It can be safely said that few features are as keenly desired as Desktop Effects. Ever since Compiz was announced XXX years ago, users and developers have been playing with the bling-tastic effects and wondering when it will hit a desktop near them. Well, the wait is no longer.

This article explains in a general sense the basic troubleshooting of Ubuntu 7.10's compiz 3d Desktop. This tutorial of sorts helps troubleshoot Nvidia cards and Ati cards. I would like to clarify the section "Possible problems for ATI users" this should be abit more clearer on new installs:

0)Install Gusty's Compiz updates ( in Add/Remove App's )

The GNU/Linux desktop can deliver a very mixed experience to the user: On one hand, you have very functional desktop environments, such as GNOME or KDE, with state-of-the-art features, capabilities, graphical effects, eye-candy and wizbang-ery (Compiz).

This tutorial shows how you can enable Compiz Fusion on an Ubuntu 9.10 (Karmic Koala) desktop (the system must have a 3D-capable graphics card - I'm using an NVIDIA GeForce FX 5200 here). With Compiz Fusion you can use beautiful 3D effects like wobbly windows or a desktop cube on your desktop.

This tutorial shows how you can enable Compiz Fusion on an Ubuntu 7.10 (Gutsy Gibbon) desktop (the system must have a 3D-capable graphics card - I'm using an ATI Mobility Radeon 9200 here). With Compiz Fusion you can use beautiful 3D effects like wobbly windows or a desktop cube on your desktop.

In Ubuntu 8.04 if you want to configure compiz manually we have a new tool called Simple Compizconfig settings manager.The OpenCompositing Project brings 3D desktop visual effects that improve usability of the X Window System and provide increased productivity.

What I ended up with was an Ubuntu box that is visually appealing to the end user while interacting with normal everyday routines. It does not slow down your machine at all and you get to enjoy many beautiful effects that compiz has to offer without fiddling with settings or self inducing the effect.

Remember when it was a big deal that Ubuntu was going to include Compiz/Beryl/Compiz Fusion out of the box? It wasn't long ago, actually, yet Linux desktop effects have come a long way since then. We've gone from desktop effects on Linux being a cool add on you could install if you wanted to do it yourself, to having it be part just another part of the Linux desktop.