Cambodia forum

For budget options I'd recommend the street with Spring GH, Burly GH, Sky Park GH.
A bit out of the way but easy access by moto to major areas ($0.50 for 1-way trip). Not yet a backpackers ghetto, friendly people and good value for money ($6 fan - $15 aircon range). However not the typical backpackers GHs with communal area where you can easily meet other travellers

Lake Area I DO NOT RECOMMEND. Some guidebooks still write positively (outdated) about this area. I never liked it but since they filled the lake it's completely hopeless with water drainage issues and rats. For a few dollars more you can have a decent room in far better areas.

Riverside area has best location but value for money is not that great there when it concerns rooms. Touristy and a great location but that's about all.

Boeung Keng Kang is a nice area as well. Caters mostly to expats with lots of restaurant and bars and some nice guesthouses/hotels.

Mid budget places are scattered all over the place. In general I think this is only worth it if you look at rooms over $40. $25-30 rooms are only slightly better than $15 rooms and not worth it (apart from location perhaps). Usually these rooms ($25-30)are in hotels that have a small restaurant, few more channels on TV and perhaps a small gym with 2 machines. Rooms look identical though.
Let me know your interests (budget, area, style) and I can name a few names.

Thanks for the suggestions! My budget is keeping within $15 or less a night. How's Boddhi Tree -- Umma?

Thanks!

Boddhi tree umma itself is fine (if not one of the best guesthouses).
My main reason for not recommending it is it's location. It's directly opposite of Tuol Sleng museum which is a long way away from anything else. You'll spend much more money on transport while I don't find the direct surroundings that great (it's not bad or dangerous though). If you don't want to do much besides spending a night in a good guesthouse it's an excellent option.