http://www.wsws.org/articles/2000/dec2000/1876-d21.shtm... I've read about it elsewhere -- somebody posted some info about this election here the other day, I don't remember hearing much about this in history class in high school, but my history teacher was one of those guys who really pushed us more on modern events, linking them to historical events as they came up -- and since there wasn't any egregious fraud in 1976 or 1980 that I can recall, he didn't lean on this one too heavily.
There were accusations from both sides about the 1960 election, of course, as well. Lots of dead people in Chicago voted for JFK; lots of dead people in southern Illinois voted for Dick Nixon and, as someone has pointed out here every time the topic comes up, the Voting Rights Act of 1965 hadn't been passed yet, so lots of minority voters who would have voted for JFK didn't get to vote.
Anybody who thinks LBJ played it strictly by the rules is dreaming. He's the guy who, during a senate run in Texas, wanted his campaign manager to start a whispering campaign about his opponent, who owned a pig ranch, that he enjoyed sexual congress with his pigs. "We can't say he fucks pigs! That's dishonest! You know he doesn't do that," the campaign manager argued.
"I'm sure he doesn't. Make the sonofabitch deny it," LBJ is said to have replied.
(on edit -- this story may be apocryphal, but from what I've heard about LBJ, it's believable enough and I've seen it repeated many times, so I can't vouch for its veracity!)
I'm quite sure there have been small pockets of fraud involved in democratic elections anywhere they're held. The ways to cheat the system always have been innumerable, what we're dealing with now is only new in that a lot of people who might be scandalized by it can't understand the technology that allows it, so it's easier for them to pretend it doesn't happen -- out of sight, out of mind.