Recently, we've come across come.in and were wondering how they do that. So, we figured that an easy way to do that would be to use the Apache reverse-proxy module and to register subdomains for each website to proxy.
On Debian, after installing Apache, the proxy modules can be enabled with:
a2enmod proxy a2enmod proxy_http
After that, a subdomain should be registered for every website you want to proxy. Then, you can create a virtual host with Apache, by placing a file in /etc/apache2/sites-available/ with the following contents:
<VirtualHost *:80> ServerAdmin mssnuggles@ted.ly ServerName k.grimore.org ProxyPreserveHost Off ProxyPass / http://kickass.to/ ProxyPassReverse / http://kickass.to/ </VirtualHost>