The best replacement for addons is plugins.

The best alternatives to addons are rated as following:
★★★★★  plugins
★  chrome extensions
★  mods
  add-ons

Your alternative for addons is not listed? Suggest!
Speaking about addons, one probably shouldn't forget about restarting firefox.

Other search terms related to addons and their ratings are:
★★★★★ restarting firefox
★★★ curse client
★ firefox
★ wow
★ google chrome
You have in mind a companion for addons and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of addons in all years. Click on graph for more.
addons
plugins
chrome extensions