Most excursions on the Rio Grande put in or end in Pilar [1].
Santa Fe Rafting Co. (888/988-4914, www.santaferafting.com [2]) runs half-day float trips and white-water runs down the Rio Grande for $50 per person, as well as three-day trips down the relatively placid Rio Chama for $375 per person.
Kokopelli Rafting (800/879-9035, www.santafeadventure.com [3]) runs a day trip through the Rio Chama’s White Rock Canyon on Class II and III rapids, combined with a hike through Bandelier National Monument [4] ($119 per person).
Both companies also do runs through the excellent white water of the Taos Box [5], with departures from Santa Fe [6].
Links:
[1] http://www.moon.com/destinations/santa-fe-taos-albuquerque/santa-fe/outside-santa-fe/the-low-road-taos/pilar
[2] http://www.santaferafting.com
[3] http://www.santafeadventure.com
[4] http://www.moon.com/destinations/santa-fe-taos-albuquerque/santa-fe/outside-santa-fe/bandelier-national-monument
[5] http://www.moon.com/destinations/santa-fe-taos-albuquerque/taos/sports-and-recreation/rafting-and-tubing
[6] http://www.moon.com/destinations/santa-fe-taos-albuquerque/santa-fe