check out my post today in the FAQ board - I saw this info in another catagory, but thought it would be useful there. Not sure it will work with Jetty, but it does work with JB2.4.4 + Tomcat 4.0.1 - in fact, if it does work with the version of Jetty you are using, why don't you reply to that message and say that it's also tested with Jetty :)
Hope this helps
Actually, the solution is different for Jetty, since there is no "EmbeddedTomcat" but I managed to find the solution.
To change the default port using Jetty, you need to change the jetty.xml file:
Making the web application the default page, i.e., http://localhost instead of http://localhost/webcams is also done in jetty.xml, by changing /webcams/* to / in the section.