Several ships have wireless.
We were on the Dawn Princess & they have a wireless card you purchased. not sure if you could access the web from your cabin but in the Atrium you could.
Oceania has wireless hot spots & now when they ships go to drydock they will have wireless in the cabins.
Cannot comment on others
Alexandr Pushkin, Carnival-Holiday, HAL-(old)Westerdam, Orient lines-Marco Polo, Royal Olympic-Olympic, NCL-Dream, Dawn-Princess, ACCL-Grande Caribe, Oceania-Insignia (3), Regatta(4) Marina (1) St Lawrence Cruise Lines-Canadian Empress
Scenic River cruise June 11,2012