At Transvirtual, before it folded, we wrote a full web browser in Java,
and released it under the GPL as part of the "XOE" framework:
http://www.kaffe.org/ftp/pub/packages/pocketlinux/
It requires some work though - it's got dependencies on the rest of the
PocketLinux framework, and Transvirtual's version of Kaffe (also in
the XOE release).
Subsequent to the XOE 1.0 release, Transvirtual ported it to run on any
JVM, but they never released that code (Transvirtual is no longer in
business).
It did a pretty spiffy job of rendering a lot of difficult web pages,
and it was reasonably fast too.
I'd love to see somebody take this orphaned code and clean it up and
make it into a standalone project. A lot of the DOM, layout/rendering
and parsing code is probably worth preserving, as it took a lot of work
to get that to do a reasonably decent job.