At first it seemed like the food situation in Phnom Penh was going to be pretty dire. Chowhound didn't have much in the way of recommendations except for higher end dining, which was not what we were looking for. And the Lonely Planet was typically useless, with listings of Mexican and Italian and other international stuff. Even worse, because our hotel messed up on our reservations, we were comped a meal at the hotel, which my instincts told me would be horrible but my companions said I was just being silly not to accept a free meal. It was, of course, horrible. So our first evening wasn't a success, food wise. But the next day we found a couple of places worth mentioning. Having wimped out on the food stalls at the Russian market - it was hot,dark and intimidating - we walked about two blocks west of the market's north end and found a perfectly excellent place on a corner with red awning with no English writing to be seen anywhere. So we don't know the name of the place but it's directly across from a large BBQ restaurant on the opposite corner. We had an assortment of Cambodian dishes, all of which were good. And the bill for 4 came to about $20.
That evening, against the protestations of our hotel manager, we went to a popular BBQ place called Sovanna 2, which was only a few blocks from our hotel. She blanched when we told her where we were going but I was not at all interested in the kind of blah tourist food that they seemt to think was appropriate. Sovanna was filled to the brim with locals, clean and efficient and had a "tourist wrangler" who helped us order stuff. Grilled pork, beef, shrimp and some noodle dish and another thing called an "equatic water plant" which was all delicious. There was a LOT of stuff on the menu that we did not order, including roasted bees and various dishes with ant eggs. The menu was hilarious and I wish I could have stolen one as a souvenir. Meal for 4 was $21.
On to the Mekong delta and then home. Great stuff all over the place - you just have to look for it.