While you can build Java applet GUIs using Sun's Swing the results are usually rather ugly and clunky looking. There's also the problem that quite a bit of programming effort will be required for even basic GUI functionality and if you want a sophisticated widgets (that is, GUI controls), you'll have to put in lots of effort.
If you'd rather make your life easier then you should take a look at Bambookit from Bambookit (see links below).
Bambookit is a 100K-byte download that runs on the Java Virtual Machine from Sun (Version 1.1.7, 1.2, 1.3.1, 1.3.1_06, or 1.4) or Microsoft (version 1.1+) under Netscape 4.06+, IE 4.0+, or any other Java 1.1/1.2/1.3/1.4 enabled browser.
The elegant thing about Bambookit user interfaces is that they are defined by scripts written in XML - this makes them easy to write, read and understand.
Babookit consists of a collection of widgets including Button, Checkbox, Radio buttons, Edit (forms), Calendar, Drag and Resize. There are also Grouped Widgets: Listbox, Tree, Combobox, Menu, Table, Splitter and Tabs as well as Prebuilt Widgets: Collapsible Panel Bar, Windows, Zooming Box, Color Picker, Toolbar, Popups and Tooltips.
(I would have provided links to the detail pages and demos of these components but the Bambookit Web site is built from frames and referencing internal pages would destroy the built-in navigation. I recommend that you just explore the site and find them for yourselves - it won't be difficult since the site is well laid out.)
What really strikes you about these tools is that they are attractive and flexible - none of that clunkiness that characterizes Swing and many other GUI tool kits.
Being XML-based also gives Bambookit some interesting management possibilities: For example, the XML scripts that define GUIs can be stored centrally and any updates then apply to the all field deployments simultaneously. And for the truly creative, an application could create a Bambookit XML script - which would potentially allow applications to reconfigure themselves.
Bambookit is priced at $700 for the first developer for deployment on a single Web site and $100 for each additional developer on that same Web site. Volume and educational licenses are also available.
Note that the company plans to release an Integrated Development Environment to make constructing Bambookit GUIs as simple as possible - release is currently scheduled for July.