Download the Chuon Nath Dictionary for Khmer for PC (works with Vista and XP) in unicode. This is a great resource, and is official.

Download it here: Electronic Unicode Chuon Nath Dictionary

Download a user-friendly installer that will install the English and Khmer SBBIC Unicode Dictionary embedded inside the Lexique Pro program (Updated 4/22/06 4406 words and phrases).
The SBBIC dictionary now includes the KhmerOS glossary - Special thanks to a the Open Forum of Cambodia and NiDA for allowing us to import the glossary. If you add entries to the SBBIC dictionary, send them to us to be merged with the current SBBIC dictionary so that others might benefit from your work. Send your dictionary to us at:

Make your own Khmer Unicode dictionary with this program by importing the knowledge base file from Adapt It or by entering in data by yourself. Khmer Unicode is supported if you configure the program correctly. You can download this program from its homepage.

This is a web site created by Chanty Sothy with an online Khmer Unicode dictionary. It has Khmer to English and English to Khmer. Currently it is best viewed in Internet Explorer.