HttpRevealer
A utility program get to see all the HTTP request/response headers. It helps to debug web applications, Flash applications and web server. [Commercial with source, trial with time and function limited]
Jazilla
open-source web browser written in Java (a port of Mozilla, aka Netscape Navigator). [Open Source, MPL]
XBrowser
Java application for browsing the web. Requires Java 2. [Open Source, GPL]