Cool Firefox plugins for mobile web developers:
MobileStartUp.com
# wmlbrowser - Add WML markup support to your browser.
# XHTML Mobile Profile - Add xHTML MP support to your browser.
# User Agent Switcher - Use this plugin to send the user-agent string of whichever mobile browser you want to emulate. Try a diverse range of user-agents to make sure your app can handle all the different formats.
# ModifyHeaders - Allows you to spoof headers. Use this to add an x-up-subno, x-wap-profile, etc. header to your browser session so your app thinks you are coming from a network operators proxy.