AGfUPX is a nice GUI for UPX with many advantages. Selecting a file using drag & drop, shell integration (adding "Open with AGfUPX" option to the context menu of exe/dll files) and redirecting UPX output to a windows dialog box are only few of them.
OzVM is a simple, lightweight, secure virtual machine. The current target application of OzVM is OzStream, allowing platform-independent self-decoding data, which abstracts encoded data from client applications.