Instead of opening your web browser and checking your Gmail account for upcoming messages, you can check your new Gmail messages directly from the Terminal using the "Curl" command line tool.
Press Ctrl + Alt + T to launch the Terminal, then issue this command:
curl -u username --silent "https://mail.google.com/mail/feed/atom" | perl -ne 'print "\t" if //; print "$2\n" if /<(title|name)>(.*)<\/\1>/;'
Replace "username" with your own Gmail username. After running this command, you will be asked to submit your Gmail account password, enter it, then hit Enter. All new messages will now be displayed in the Terminal.
Note: This tip is tested under Ubuntu 11.04/10.10/10.04.