You can use this applet on your site for your channel. You can link it like that :
<a href="http://target0.be/irc.php?chan=yourchan&nick=yourvisitor???">Link</a>
"yourchan" is the name of your channel without the #, and "yourvisitor???" is the nickname of the visitor,
as you may have guessed. Note that each ? is replaced by a random number.