I use a traffic script and webmasters can add themselves in. It basically serves as a top list using cookies to track traffic.
Other sites use other kinds of scripts like ones that look at server stats and build lists from that.
Still others do "hard link" trades where two sites just agree to display each other's links.
Look around on site's webmaster's page for traffic trades or try posting here asking for trades.
http://www.greenguysboard.com/board/...une=&forumid=4