There was an earlier thread regarding photography in Siem Reap / Angkor Wat. I found this link some time ago and thought I'd share it with you guys.
Peace of Angkor is a English-run guesthouse in Siem Reap, run by photographer(s). They organize photography trips. They have an extensive list of trips, half day, a full day, or a few days. The ones going into outlying stilt villages in the middle of mangrove forests, or remote villages and Angkor Temples, are especially worth it because it can be quite hard to coordinate these trips on your own.
Be sure to see Banteay Srei and Kbal Spean (Valley of 1000 Lingas) and the jungle temple of Beng Melea (this one is even more awesome than Ta Prohm, the one Tomb Raider was filmed in)!