Favorite sites Facebook, Gmail, YouTube,or Yahoo are blocked at your school, college or at your work place, then you would rely mainly on web proxies.
The proxy sites not only allow you to unblock the blocked websites at your school, college and at work place, but also help you to browse anonymous on non blocked websites.
It would would be always better to use SSL based proxies. Also, use https browsing for your GMail, YouTube or Facebook if you access them through proxies. This would prevent your GMail or Facebook account password get stolen.
SSL proxies which I had tried are,
There are many sites that offer web proxy service for free. But there is a chance that even the proxy sites may get blocked if the network administrator notices your activity. Then you may have to ponder new proxies, may be once in few days!. I found one interesting site which lists some new random proxy sites. So you can rely on a new proxy site, even if existing proxy site is blocked.
Add the list of other proxy sites in comments, if you have tried and found them useful.
Related: Watch YouTube if blocked at school, college and workplace