GTDInbox Firefox Addon for Gmail

URL : GTDInbox
Description : GTDInbox is a powerful addon that will transform your Gmail inbox into an all in one manager that can compete with Outlook. You can do your most common functions within one or two intuitive clicks using a popup command box that allows you to preview, archive, delete or modify the labels of your emails. Another great feature is that you can mark emails as actions to be completed and given priority. Process actions by project, context or person.

Categorize actions, communication and resources?the features are seemingly endless, marvelous tool.

Better Gmail 2 Firefox Addon for Gmail

URL : Better Gmail 2
Description : Add useful extra features to Gmail, like hierarchical labels, macros, file attachment icons, and much, much more. Better Gmail 2 compiles the best Greasemonkey user scripts for Gmail into a single package.

tLo : Gmail Manager Firefox Addon for Gmail

URL : tLo : Gmail Manager
Description : This is a Firefox extension that allows you to manage multiple Gmail accounts and receive new mail notifications. Displays account details including unread messages, saved drafts, spam messages, labels with new mail, space used, and new mail snippets.

Gmail Skins Firefox Addon for Gmail

URL : Gmail Skins
Description : This cool allows you to customize the look of your Gmail inbox. Gmailskins adds the following features: Change the color/skin of your inbox, integrate your google homepage alongside your inbox (this allows you to view weather reports, rss feeds, news headlines, flickr recently added, google calendar module etc from your inbox), insert images from your Picasa web album in to your emails, insert smileys/emoticons, insert HTML tables and other complex HTML in to your emails, make the navigation (Inbox, Starred, Sent Mail, etc) appear horizontal, fix the navigation in place so that you don’t have to scroll t