Below is a video for all hidden coins by Damien Fate on his YouTube channel. I take no credit, but thought I'd share it as they're hard to find in some levels.
World 1: 11, 13, 15, 21, 23, 24
World 2: 27, 29, 30, 32, 36, 44, 49
World 3: 52, 56, 58, 59, 61, 62, 65
Coins can be found in each of the above levels, and to register them as collected, you must finish the level after collecting the coin. In the level select screen, a coin will appear above the level number to show that you've found that coin in particular. Happy hunting and try not to rage too much.