I've created Firefox and Chrome addons that allow you to block certain sites. For instance, you could block:

- google (this would mean www.google.com, mail.google.com, images.google.com,... are blocked)

- mail.google.com (only gmail)

- google.com/reader (only google reader)

If you wanna try the addons, the URLs are:

Firefox: https://addons.mozilla.org/en-US/firefox/addon/no-procrastination/

Chrome: https://chrome.google.com/webstore/detail/gigmkhkildapllnjbnkfgknkkjeohkmo

Let me know if you encounter any issues.

Thanks!