Potato is a Squeak virtual machine completely written in Java. It is a derivative of JSqueak (http://research.sun.com/projects/JSqueak/) which was developed by Dan Ingalls. There is a blog on the project at http://potatovm.blogspot.com/.
Pocket Smalltalk is Smalltalk-80 for small machines. Currently we support PalmOS with a virtual machine. We are looking for ports to other devices. PSt consists of an IDE (currently for Win32), which generates executables from Smalltalk source.