I do most of my development in VMware Workstation (version 7 at the moment). Unfortunately, on my laptop with 4 GB of RAM, an OCZ Vertex 2 240 GB, and a Core 2 Duo T9550 (2.66 GHz) does things criminally slowly when there's more than one VM running at a time (which given that I've been doing multi-server development lately is most of the time).
I know that there are some processors which (for example) have specific features to make virtualization fast, and I think there are some chipset features which make memory access faster specifically for virtualization workloads, but I'm not positive on either of these, and even if they do exist, I'm not sure they're available on laptops.