The first time I came across this place was on a street art tour with the guys at Graffitimundo (a street art tour company).. I was impressed on first glance and was even more impressed when I made a return for their 'Carton Pintado' exhibition recently (an exhibition with painted cardboard in 50s-style art).
Hollywood in Cambodia is a creative space that often exhibits really cool street art. The gallery sits above 'Post bar', a humble bar with graffiti painted all over its walls. So, once you're done with the creative stuff, you can sit and enjoy a beer. It's a lot cheaper than other bars in the area and theatmosphere often feels very relaxed.
Go on a Thursday for free pizza with your beer (although do note that the gallery is only open at weekends).
Fr-Su: 14:00-18:00