Here’s a cool firefox extension for Gmail addicts called Gmail Manager. Gmail Manager allows you to manage multiple Gmail accounts and receive new mail notifications. Displays your account details including unread messages, saved drafts, spam messages, labels with new mail, space used, and new mail snippets.

• Manage multiple Gmail accounts
• Receive new mail notifications
• Support for Gmail hosted accounts
• Ability to import/export account preferences
• Tooltip with account details and new mail snippets
• One-click access for loading your Gmail account
• Mailto: links detection
• Quick mail compose for Gmail accounts
• Customizable icon placement in the toolbar/statusbar

Link: tLo : Gmail Manager