They do have PCIe to ZIF adapters, for say adding a 1.8" Hard Drive. . .
http://jkkmobile.blogspot.com/2009/04/pci-e-to-zif-adapter-for-eee-pcs.html
and you can get an adapter...
http://www.r3cube.com/r3cube///index.php?act=viewProd&productId=42&ccUser=
Btw I believe someone did mod their...