Cambodian Rural Development Tours (crdt.org.kh) runs a number of homestay opportunities along the Mekong, offering one- or two-night stays at a trio of villages up and down the river and allowing visitors a rare chance to experience traditional Cambodian rural life from the inside.
Koh Pdao Just north of Sambor (and 40km north of Kratie). One- or two-night homestays on this peaceful river island, including visits to the nearby turtle conservation centre, the hundred-pillar pagoda and the dolphins at Kampie.
Koh Preah Village 35km from Stung Treng. Visits include cycling along the Mekong, the chance to sample traditional Khmer village food, a visit to the local dolphin pool and chats with village elders.
Preah Rumkel North of Stung Treng near the Laos border. Visits include kayaking, cycling and dolphin-spotting.