There has been much excitement about Robert F. Kennedy, Jr.'s article "Was the 2004 Election Stolen?". The thesis he argues for is that "Republicans prevented more than 350,000 voters in Ohio from casting ballots or having their votes counted -- enough to have put John Kerry in the White House." Now he has followed up by announcing that he "plans to file 'whistle-blower' lawsuits against two leading manufacturers of electronic voting machines."
This still-unproven charge is not new. British reporter Greg Palast has written "How They Stole Ohio -- And the GOP 4-step Recipe to 'Blackwell' the USA in 2008". He's been on this story for years now, with articles about the 2000 race like "The Great Florida Ex-Con Game -- How the 'felon" voter-purge was itself felonious".
The best place for daily updates of the fight for honest elections across the country (including the hot recount in southern California over a special Congressional election just narrowly won by Republicans, after massive illegalities and with unprovable results) is at The Brad Blog. Some groups active in this struggle include Velvet Revolution, Black Box Voting, Verified Voting, and VoteTrustUSA.
This issue is also coming to a boil just across the Rio Grande, where all indications are of massive messups in their Presidential election. Palast is on the case there too, with "Grand Theft Mexico" and "Mexico and Florida have more in common than heat". The alleged loser, Lopez Obrador, has promised an appeal of the questionable results to large crowds, and some of the Mexican press itself is doubtful.
Meanwhile, one US paper recalls the issues at stake in "To many of Mexico's poor, election a setback", and another notes the importation of nasty US campaign techniques in "So has Mexico been taken for a ride on a swift boat?", with a link to youtube video of a (Spanish) TV ad which shows their point. So far, the best single English blog I've found for coverage of this crisis is El Machete 2006.