Oldham stunned Premier League champions Manchester City at Boundary Park, while there were comfortable wins for West Brom and Queens Park Rangers.
Norwich claimed a creditable draw against Ajax and Derby edged a seven-goal thriller with Northampton.
Manchester City welcomed Joe Hart back into the pre-season plans following his efforts at Euro 2012, but he was beaten after just two minutes as the Blues suffered a 2-1 defeat at Oldham.
Robbie Simpson broke the deadlock, only for Roque Santa Cruz to restore parity.
Oldham were not to be denied a prized scalp, though, and grabbed a dramatic winner in the dying seconds through Jonathan Grounds.
Norwich took the lead against Dutch champions Ajax at Carrow Road through Anthony Pilkington, but were forced to settle for a 1-1 draw as Lasse Schone levelled matters.
Queens Park Rangers made light work of Wycombe, with Jamie Mackie, Shaun Wright-Phillips and Nedum Onuoha on target in a 3-0 win for the top-flight outfit.
Saido Berahino bagged a brace as West Brom stepped up their pre-season preparations with a 4-1 mauling of Stockport.
Tongo Doumbia scored on his Wolves debut as they hit back from two goals down to pick up a 2-2 draw at Shrewsbury.
Robert Earnshaw and Peter Whittingham were among the goals as Cardiff eased past Cheltenham 4-0.
Sam Collins earned Hartlepool a 2-2 draw with Middlesbrough, while Ipswich were undone by a Kane Ferdinand double in a 2-1 defeat at Southend.
Theo Robinson netted twice as Derby prevailed 4-3 over Northampton, with a late rally not enough for the hosts.
Charlton hammered Bury Town 5-1, while Akpo Sodje grabbed two goals in a 4-1 victory for Preston over AFC Wimbledon.
Doncaster picked up a morale-boosting 3-1 win over Hull City and Burnley won by the same scoreline at Bath.
Coventry slipped to a 4-1 defeat at Wrexham, Exeter held Torquay to an entertaining 3-3 draw and John Cofie grabbed the only goal of the game as Sheffield United saw off South Yorkshire rivals Rotherham.