It was true once, prior to 9/11, you could show up at the port and catch open cabins. My parents lived in Orlando and my uncle in Miami so they'd go down to Miami and use my uncle's place as a base to try to catch a cruise out of Miami or Ft Lauderdale. I'd get these last minute calls from a terminal that they were off on the MS Whatever for X number of days and they'd call when they got back. Their success rate back then was actually pretty high as they weren't picky about what deck or cabin category. Knowing my dad it would be the cheapest he could get and still get on the ship. In their case his health issues actually caught up with him before 9/11 happened so they had to quit the standby routine around 1996.

Port security and passenger manifest requirements today make it virtually impossible to be a "terminal rat" today. The modern version is more like waiting for a last minute email, periodically visiting an Internet site, or having a good TA to watch for deals. Of course for us living in Texas pretty much means we have to fly to cruise ports, with the exception of Galveston, so as mentioned the last minute airfare are really deal killers for us. There is also a recent trend that cruise lines are starting to institute policies where they will not drop fares within 30 days of a cruise. I know from Cruise Critic a number of various cruise line "loyalists" have been complaining about what became this glut of "pennies on the dollar" deals over the past few years and, as ktremor posted, it looks like some lines are responding. Some are even cutting off incentive packages and not offering them within 30 days of the cruise.