There are plenty of them.
Which one would you recommend?
Is there one which notifies about unread buzz posts?
gm-notify : https://launchpad.net/ubuntu/+source/gm-notify
It integrates best for notifying, but not for managing the e-mail straight from it (like checkgmail) or describing the content of the e-mail after the notification.
This is the one I use and works perfect: https://launchpad.net/ubuntu/natty/+source/gm-notify/
There is also this one which I tried and also works good (Include gmail, reader, etc..): http://sourceforge.net/projects/googsystray/
So you have a choice of a pop balloon like or a small icon in tray that notifies you.
I use WebMail Notifier
- it's a firefox extension. When new mail comes (and you have firefox turned on) - small message pops-up at the bottom rigth corner of the screen. You can click that message - and it drives you do gmail in a new tab.
Also it has a small notifier - which you can place in a firefox toolbar - and it shows wither you have new mails.