If you don't use offline gmail, it is easy to access 2 or 3 gmail accounts from the same browser.
You even can have 2 tabs open, one for each account.
You just have to click on your email address on the top right of gmail screen, then on "Switch account", then "Sign in to another account" or directly the account name if you are already logged.
The first account you log in is accessible through this link : https://mail.google.com/mail/u/0/#mbox
The second : https://mail.google.com/mail/u/1/#mbox
The third : https://mail.google.com/mail/u/2/#mbox
If later you log in a different order, the links will reflect the new order.
The full article on Google BLog is at http://gmailblog.blogspot.com/2010/08/access-two-gmail-accounts-at-once-in.html