Linux box as Gateway

Hi everybody I am a newbe in Linux, maybe my question will be to stupid for you but, actually I am trying to use our linux box as a gateway to connect our small lan to Internet, actually fetchmail and sendmail are working fine also squid for http, but we need another protocols. does anybody know where can I find articles on configuring this box as a gateway or maybe how to set up a socks proxy server TIA Manuel p.s pardon my bad English but it is not my native language