The monthly NPD charts are handy for retail sales, but for digital sales? Useless! They're not covered. No, for that stuff, we rely on PR mailouts, like this one from Sony.
Provided to the Gamasutra network, this list shows the ten best-selling PlayStation Network titles for April 2009. Rag-Doll Kung Fu is at #1, and that's before it was given away for free, so it should retain the top spot next month as well.
Further down the list, Flower continues to do well, as do other PSN stalwarts like PAIN and Mortal Kombat II, though PS3 owners fascination with Noby Noby Boy seems to be fading fast.