If you use multiple Gmail accounts like me based on your needs. Generally to use multiple accounts we use separate browsers for each. But this is not a long-term solution. So if you are a Chrome user then a tiny extension, Google Mail Multi-Account Checker will help you with all.
Google Mail Multi-Account Checker chrome extension keeps you updated to all your Gmail accounts from the same browser window and even without constantly switching them. As per the name suggests, the keeps track of your multiple Gmail accounnts and notifies you about the new Gmails in the browser toolbar.
Installing the extension will show up a new button on browser toolbar and clicking it will popup a window which displays all your unead messages from multiple Gmail accounts and clicking on any individual email will open the Gmail page in your browser.
You can easily configure upto 9 Gmail accounts in the extension from the Options Page. The Only major con about the extension is that it saves your accounts password in a plain text, So you might not want to use it in a shared computer.
Download Google Mail Multi-Account Checker