Michael

allisonflyer beat me to it: I was also going to recommend Kampot and nearby Kep. I was down there a few weekends ago and, though it has changed quite a bit in the last few years, it remains my favorite provincial capital. Kep is also close by (20-30 minutes) and the lodging options there have improved immeasurably in the last couple of years. Both places have great (though different) scenery, decaying but beautiful architecture, fantastic seafood, and a very relaxed lifestyle. You can stay in either place and see the sights of the area -- or stay 1-2 nights in each place.

In addition to the Tales of Asia website (which is now a bit outdated), I would check out the advertiser-supported Canby Publications guide sections on Kampot and Kep, (especially good for their maps, transport info and general descriptions). Also, the NYT just ran an article on Kampot and Kep a few weeks ago (as well as one on Siem Reap).

Re: travel between Chau Doc and Kampot/Kep, I know that there are a number of independent tour guides and hotels/travel agencies that advertise transport directly from Kampot/Kep to Chau Doc -- and so I imagine that you can do it in the other direction. But you might want to contact one of the agencies / guides in advance, and arrange to be picked up. I don't know how much a car from Chau Doc to Kampot/Kep costs, but it should be in the neighborhood of $15-$25 o/w (for the whole car, not per person).

Please feel free to let me know if you'd like more information.

Happy travels,
Michael