Review for Extension List Dumper by DarthNinja.
Rated 4 out of 5 stars
I like the idea for sending a list of your plugins for debugging purposes (or if you want to purge your profile and re-install everything), but there's a better way to back up your plugins / addons (also a good way to keep profiles on 2 pcs the same).
Just copy the "Firefox" folder from C:\Documents and Settings\*USER*\Application Data\Mozilla to another folder, inside is everything firefox uses when loading a profile, just copy the folder back if you ever need to restore your stuff.
note that you may want to compress the folder (mine is 120mb compressed to 23).
To create your own collections, you must have a Mozilla Add-ons account.