US-Pirates are very active on halloween. Most used frequency range is between 6800 Khz and 7000 Khz. Some use SSB Single Side Band modulation. Watch out the Grapevine under http://www.frn.net/vines/ were listeners and stations meet. A good idea is also to visit http://www.blackcatsystems.com/pirate/ were you can join the IRC-channel #PirateRadio and surf on some links. Happy halloween hunting !
In Europe US-pirates were mostly heard around 2300 Utc and 0300 Utc on the 6.9 Mhz band.