Before going to the long list of proxy sites, i have a different solution to bypass Network Security Firewall.

What you can do is get a pen drive, download Portable Mozilla Firefox Browser or Portable Google Chrome (whichever you like)from the links below.

The best part is you can run it like you are using it normally, there is no change you gonna feel. I personally will suggest you to try this first..

Download Portable Mozilla Firefox or Google Chrome in just few minutes from here..

If the above technique is not working in your case, here are the list 60 Proxy Sites you can use to bypass most of the Network Security Firewalls