The most basic thing to try first are websites which run proxies for you. These are most likely blocked by your firewall too, but it's worth checking. This is quick and it'll stop you chewing off all your nails. Keep in mind your firewall probably also blocks URLs with the word “proxy” in it.
Take a look at these:
If these aren't working, try this fantastic list of free web proxies which is rated and updated all the time.
Google+ and Google Plus Unblock Proxy FreeGoogle+ and Google Plus Unblock Proxy
Google+ and Google Plus Unblock Proxy
Google+ and Google Plus Unblock Proxy
Google+ and Google Plus Unblock Proxy