How do I create a basic GUI for something like a data-entry application, a la WindowBuilder, Visual Basic, etc.?
The base Squeak doesn't really include a GUI Builder or Widget Kit for data-entry applications, although it does have quite a few widgets. There are a few external Widget Kits/GUI Builders available which can be used with Squeak:
SqueakGtk is an attempt to port Gtk+ GUI in Smalltalk Squeak. (Last known news circa 2008)
wxSqueak is a Squeak interface to the wxWidgets (formerly known as wxWindows) GUI library. (Last known news circa 2005)
BobsUI is a data-entry UI widget set for Morphic which contains a Rolodex example. (It does not include a "GUI builder"... you must specify the widget layout in the source code.) It does support tabbing between entry fields, and a few other niceties. BobsUI has been used by a number of people and has been relatively active in terms of being updated to the latest Squeak versions, and is available on SqueakMap. See the BobsUI swiki page for current downloads and more information. (Last known news circa 2006)
Prefab widget set is a 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.blit.ca/prefab.html. (Last known news circa Squeak 3.2 release)
CGUI is a set of Morphic Widgets written by Squeak people. It has a modern Design, mouseOver Effects and always an Example of using it. (Last known news circa 2006)
Bricks from Todd Blanchard has the potential to be a very useful set of building blocks for creating a Morphic UI. Current version is for 3.6. (Last known news circa 2006)
SguiKit (Squeak GUI Contruction Kit) is a Morphic widget contruction kit from Michael Rueger. It lets you layout widgets with a contruction tool, which then generates a gui spec. However, it has not been ported to newer versions of squeak (3.0 and up, and maybe nothing past 2.7). See http://www.squeaklet.com/sguikit/index.htm.