SeaMonkey Extensions compatible with version 2.2 for any regular user. If you are missing any, then it is not compatible. Of course, this is not exhaustive list, so visit frequently for any inclusion.
Add a compact menu button to the navigation toolbar, and hide the menu bar.
Identity Chooser helps you to always use the correct identity when composing a new email.
Firefox based theme for SeaMonkey 2.x
This Add-on allows to have HTML temporarily allowed in the currently displayed message by only one click. When switching to another message, it'll be shown automatically again in plain text or simple html mode (if this is your default mode).
See more search results etc. on one page, concatenating several pages together...
Adds extension options dialogs to the Tools or Titlebar menu and includes toolbar icon.
CS Lite allows you to set the permission of the cookie every domain from toolbar.
Allows to copy selected text as plain text by adding a 'Copy as Text' menu item to context menu.
Launchy will enable you to open links and mailto's with external applications...
Open links, pages, and bookmarks in any other browser, using right-click context menus or with one click of the drop-down or standalone toolbar buttons. Modify any menu, browser name or location. Incognito/private browsing mode is also supported.
Remembers last selected (hilited) extension/theme/plugin/userstyle in Add-ons Manager. Turn off/on the add-on selection list box and/or fine tune behavior via its Options.
Adds submenus for flipping or rotating to the image context menu.
Resize 'Add Bookmark' Popup / 'Edit This Bookmark' Popup, fixes tree selection bug, option to disable popup auto close & Update Url and/or Name of a bookmark with the Url/Title of current page.
Replacement of OpenBook addon
Adds a Tabs menu to the main menu that lets you easily change between tabs.