When you work at a company that won’t let you browse Facebook or any other itchy site. OS X comes with a utility called SSH (secure shell).
With it you can setup a secure encrypted channel between 2 machines and browse anything you want without IT department knowing about it.
What you need is a machine with SSH and a valid user account (Your home Mac ). Fire up a terminal on your work machine and enter.
ssh -ND 9999 -v userName@machine.com
This will setup the secure channel between your work machine and home machine. Anything you send to port 9999 on your local machine will be encrypted and forwarded to your home machine, from there it will travel unhindered to its destination.
Effectively by passing any Firewall or blocking rules your IT department migth have.
Now you have your secure channel things will not work magically. You need to set your browser to use the proxy you just setup.
Go to your browsers proxy settings
Preferences -> Advanced -> Proxy -> Change Settings -> Socks proxy
Preferences -> Advanced -> Network -> Connection settings -> Socks proxy
Set your proxy ip to 127.0.0.1 and port 9999
You are set now, any thing your IT department will see is garbage going to/from your machine at home and machine at work.
For Firefox users there is a plugin called FoxyProxy which will let you use the proxy only when connecting to blacked list sites. Since proxy is a little bit slower than your local network it will speed up your overall browsing exprience.