Virtual Machine optimizers

VMware does have built in tools for shrinking Virtual Disks.

And you can also use the VMware Virtual Disk Manager to do this.

A lot of supposed optimizers just make it easier to remove unnecessary software/services from Windows--items that can be removed manually (for free) by the user.

I agree with Dave Webb's suggestion for using VMWare's built-in tools. In addition, I keep a bare-bones image (whether it's XP, Vista, or Windows 7) with as much of the bloat uninstalled/disabled. I'll use the bare-bones image as a base for subsequent clones.

The biggest optimization IMHO is ensuring that your VM isn't fragmented.