A new libwww application - Charlotte:

For real Web applications, the next generation of Charlotte is
now available from   http://www.igs.net/~mjw/xgd/ along with
many more details.

Charlotte interacts with the web using HTTP  just like familiar
browsers, but instead of rendering textual Web pages from HTML, 
it renders a GUI from XML.  Charlotte uses the client's native
platform for rendition of the widget set.

Charlotte offers far more interactive capability and control than just
the typical browser's one-shot "point-and-click", and any interaction
can result in new GUI content and appearance.   GUI actions can
trigger http requests, which can be serviced by common cgi-bin
handlers, or GUI actions can be used to automatically synchronize
data with arbitrary hosts, or refresh any element of the GUI.  
Cheers,

Mark