If the entire site is blocked by your ISP or is controlled by that site based on the country you live in, then you simply bounce off a computer set up to be a proxy server (in the case of entire countries you pick a server outside your country). Most of these want to sell you the service but many allow free use. Some try to force you to pay for popular sites like piratebay, so if one doesn't work try another.
I am not recommending this particular site, just using it as an example of how you can find a huge list of sites which may suit your needs:
Proxy.org I have found it is usually easier to click on one of the sites in the list and enter your address in the sites webpage rather than to try to enter a URL on that page and bounce with the GO button. For more places to try, simply type "proxy server" into your search engine.
Note that these are for small amounts of data such as a website html or a torrent header; you won't be allowed to download movies, etc. This is of course slower, as every link in the html is editted to be linked through the proxy. Some have settings (either right on the screen or under an options or settings link) and you may need to enable or disable such items as scripting and cookies in order to get your particular website to work. Many just aren't very good at converting the links or are very slow; when in doubt try another.
Dave, maybe try something like
here
DISCLAIMER:
If you use this to access porn from work - it's your own head so don't blame me; most job sites log internet use and this isn't hiding what you do, it just makes the links a lot longer but not untraceable. I used to use this to access eBay from work years ago .... ahh, good times.
Oh just a little history.
Early on, roughly 10 years ago or so, one of the first of these sites was available for public use but the CIA loved it so much for their agents in the field that they bought it and took the site private. Now 10s of thousands of these sites exist.
BTW, governments like China try to block these proxy sites as well because the citizens can use them to get around restricted websites such as porn. Something you may want to consider if you have children you are trying to block sites from. I know in norton there is an option in the parent minder for proxies but what is funny is the kids may know what a proxy server is and the parents don't, so they don't bock it.