About two years ago I wrote a little crossword extension for Firefox. I made it available through the Wizz RSS forum, but never uploaded it to AMO. In the meantime, having the wonderful memory that I have, I forgot all about it, until a few days ago when someone emailed me asking if it was still available. I dug through various backups and found the code 
Anyway, I’ve made a few changes to the code and I’ve uploaded it to AMO. Not that it’s anything mind-blowing, but maybe a few people will find it entertaining.
Crosswords is in the AMO sandbox and can be installed from https://addons.mozilla.org/en-US/firefox/addon/8372
If you install it, please take the time to review it, as reviews are (Seemingly) the only way of getting an extension out of the friggin’ sandbox.
The extension hooks into an online database of crosswords. Currently there are only three crosswords in the online database. I’ll add a few more crosswords to the database soon. As new crosswords are added to the online database, they will automatically become available to the extension.
Here is a preview of what Crosswords for Firefox looks like (Click to view full size): -
