I just needed to do this, since Oracle 10g XE Web Interface also listens on port 8080.
After a quick lookaround in its folders, I found a way.
So here is how it is done:
Stop Tomcat.
Go to <Your Tomcat Directory>/conf/
Edit server.xml there.
There will be a Connector tag there.
<Connector port=”8082” protocol=”HTTP/1.1″
connectionTimeout=”20000″
redirectPort=”8443″ />
Change its port attribute to anything you like; in my case it is 8082 as you can see.
Restart Tomcat.