The Efika MX smartbook (http://www.genesi-usa.com/products/smartbook) is a small and lightweight device. Much bigger than a Zaurus but still quite nice. Soon they will have a version with built in 3G.
Or, you could try their Efika smarttop (http://www.genesi-usa.com/products/efika) which is the same thing but without a screen. It is bigger than a Zaurus but not a lot bigger. I can definitely foresee myself owning one of these, I just need to find some spare cash.
They have an active developer program too with some interesting projects (http://projects.powerdeveloper.org/program/imx515/blogs).