United States English Spellchecker for Firefox, Thunderbird and SeaMonkey by Kevin Atkinson and Geoff Kuenning.
To enable, right-click in a multi-line text box, select "Languages", then "English (United States)".
Xmarks is the #1 bookmarking and open tab add-on. Keep your bookmarks, and open tabs backed up and synchronized across computers and browsers. Mobile phones with Premium access. Utilize LastPass to sync passwords!
Display all Google services as buttons or as a space-saving dropdown menu next to your address bar. Reach services like Gmail, Google reader, Google maps, Google calendar, and many more in a single click from your browser.
After the Deadline is an intelligent grammar, style, and spell checker. It works with most web sites.
Collections are groups of related add-ons that anyone can create and share.Explore Collections