Morphic is a direct-manipulation User Interface (UI) construction kit based on display trees. It works with graphical objects called Morphs. It replaces the original Model View Controller graphics toolkit of Smalltalk-80.
Morphic Wrappers, which lets you wrap any object and drop it into a morphic world.
(linked page contains dead link to old MathMorphs site. MathMorphs is being revived but does not currently have info on Morphic Wrappers. MathMorphs can be found here: http://community.ofset.org/wiki/MathMorphs_Revival_Project)
Prefab is a new Morphic UI widget kit by Chris Reuter, which lets you layout widgets on the screen and then generate Smalltalk source code from this layout. It includes various standard (data-entry) widgets, and is roughly based on Tk. See http://www.sentex.ca/~chrisreuter/prefab.html