My two new favorite firefox plugins:

  • firebug: Combines so much useful functionality that I used to use multiple plugins for before, plus more that is not avaiable elsewhere. Basically lets you dynamically see sections of your page (css, html src, dom, etc) when you mouse over, regardless of if that section was generated dynamically with javascript!

  • Tamper Data: Lets you see request/response headers/data like the Live HTTP Headers plugin, but also lets you mess with the data before submitting it back to the server.