Almost all Minecraft sites use a captcha:
http://minecraftservers.org/
http://www.minecraftservers.net/
http://minecraft-server-list.com/
http://minelist.net/
http://mineservers.com/
http://minecraftservers.biz/
http://www.mc-index.com/
http://topg.org/Minecraft
http://mcservers.org/...