Siphon will manage and sync all your Add-ons with your different computers. It will also save your Add-on list if you ever need to reinstall Firefox.
Siphon is still in the beta period. Please let me know about your experience, any problems you have, what you would like to see, and also what you like. Help Siphon evolve.
Siphon API
Siphon can be configured to use 3rd party servers. View the Siphon API documentation for more information on how to configure a Siphon server.
News
July 26, 2010
Siphon 0.9.0 released, pending approval from Mozilla.org.
January 29, 2010
TaranFX.com
January 24, 2010
FansOfTech.com
June 16, 2009
RGPTech