http://popunderexchange.com/ a Popunder Exchange with a 2 to 1 starting ratio which is increased in some instances.

http://trafficmultiplier.com/ offers a capped exit traffic popunder exchange on a 3 to 2 ratio.

http://www.exittraders.com/ a popunder exit exchange with a 5 to 4 exchange ratio.

http://www.freevisits.com/help.htm operates a 2 to 1 ratio popup exchange as well as a banner exchange.

http://www.w3exit.com/ a 2 to 1 popunder exit exchange for webmasters which delivers 1 capped popunder per visitor.

http://www.exituniverse.com/ provides a popunder exchange with a 2 to 1 ratio and 750 credits upon sign up, might be uncapped.

http://www.123exit.com/ a 4 to 3 ratio popunder exchange that loads the popunder when a visitor first visits a site.

http://www.tcfb.com/adnetworkfront.html a 2 to 1 popunder exchange program.

Free Christian Internet Traffic - an exit popunder exchange with a 3 to 2 exchange ratio for Christian themed websites. Company also operates an affiliate program for Christian themed merchandise.

Casino Exit Exchange - an exchange site for gambling sites offering a 2 to 1 ratio on popunders. Exchange will buy your credits if wish as well.