It's a pretty big, hectic city. I spent 4 nights here and 3 of them were for the water festival, so I don't have a particularly good view of what the city is like normally. I stayed by the riverfront which is probably the area of choice. There are lots of good food options (see below). I don't think more than one day here is really necessary, just enough time to do the Killing Fields, S21 and have some good food.
Oh and I'm pretty sure that you pronounce it "P'nom Pen", even though plenty of tourists call it "Nom Pen".
Accommodation
The Artist Guesthouse
The first place I stayed at in Cambodia. Probably the nicest room I've had on my entire trip but I paid extra (I think maybe £25) because it was all very last minute and I was there during the water festival when accommodation choices are limited. Very helpful staff.
Bright Lotus Guesthouse
Right behind FCC, it has basic rooms but it's cheap and perfect location.
Food
Friends
Possibly the most famous social enterprise restaurant in the country. It claims to be tapas but the dishes weren't particularly small. Tasty food and a great cause. It gets very busy so either book ahead or get there early as queues are normal.
Romdeng
Sister restaurant of Friends. Has adventurous things like tarantulas and red ants. I had both.
Nightlife
FCC (Foreign Correspondence Club)
Great building on the riverfront. Good for drinking while watching the streets from above.
Sights & Activities
The Killing Fields
It has to be done but it's not exactly enjoyable. The audio tour is very informative. It's roughly a 30 minute tuk tuk ride from the centre. I rented a tuk tuk for the day to take me here and then S21, waiting for me at both places. This is the one time I overpaid, I think I paid $20 (the 'standard' rate, even told to me by my accommodation) but I'm quite sure that was too much.
S-21 (Tuol Sleng Genocide Museum)
I did it straight after the Killing Fields, which was probably a mistake. I didn't get a guide which was also a mistake.
Aeon Mall
This might be the only time I'll ever put shopping in a guide because I normally hate shopping but after spending nearly 4 weeks in remote places, I really enjoyed going to this big modern mall. I especially liked the cinema on the top floor with its '4D' screen. I think I paid a couple of dollars to get here, maybe even $1 - this was once I'd got a full grasp on Cambodian prices and their haggling.
Food
Please use my Cambodia food guide which has all of my favourite places and dishes for the best food in Phnom Penh.
Accommodation
The Share Phnom Penh Hostel
Nice modern dorms for $8 per night. Not perfect but the location was good and the staff were lovely.
The Artist Guesthouse
The first place I stayed at in Cambodia. Probably the nicest room I've had on my entire trip but I paid extra (I think maybe £25) because it was all very last minute and I was there during the water festival when accommodation choices are limited. Very helpful staff.
The Bright Lotus Guesthouse
Right behind FCC, it has basic rooms but it's cheap and perfect location.
Nightlife, bars & cafés
FCC
Great building on the riverfront. Good for drinking while watching the streets from above.
Cerevisia Craft Brewhouse at Botanico
Open air bar, so it can be hot during the day but they have plenty of fans.
Tasting of 3 small glasses: $4
Regular (330ml): $3.50
Large (473ml): $4.75
They seem to have 8 beers on tap. Cash only. Nice staff and owners.
Hops Brewery and Craft Beer Garden
Really huge place, with seating options inside (with A/C), outside and upstairs. Friendly staff. They brew on site following German purity laws.
I had the tasting plank of their 4 beers plus the guest cider ($10.89 inc tax). They were ok but not particularly to my tastes.
Note that they add tax to the bill at the end, which I'm not a fan of at all.
BattBong
You enter the bar through a Coca Cola door. Apparently it gets lively at weekends with live music.
Himawari Microbrewery
A tiny craft beer brewery which is part of a fancy hotel. Happy hour is 4pm - 6pm and is 30% off. I only tried the American IPA and it was better than I was expecting. There are seats outside by the river which had a nice breeze while I was there.
Sights & Activities
S-21 Tuol Sleng Genocide Museum
I did it straight after the Killing Fields, which was probably a mistake. I didn't get a guide which was also a mistake.
Aeon Mall
This might be the only time I'll ever put shopping in a guide because I normally hate shopping but after spending nearly 4 weeks in remote places, I really enjoyed going to this big modern mall. I especially liked the cinema on the top floor with its '4D' screen. I think I paid a couple of dollars to get here, maybe even $1 - this was once I'd got a full grasp on Cambodian prices and their haggling.
The Flicks Community Movie Theater
Small cinema with a daily rate to see multiple movies.