Workona - A better way to work in the browser.
Auto Tab Discard - Auto Tab Discard a lightweight extension that uses the native method (tabs.
Session Buddy - Manage Your Browser Sessions
Firemin - Firemin will force Firefox to use less memory. It is safe to use, spyware free and completely free.
Toby - Better Than Bookmarks
Total Suspender - Total Suspender is a platform that comes as an extension for the Firefox browser to suspend the processes of tabs.