Taos is one of our favorite places. Here are some things to see and do in the area: The Kit Carson Museum is worth a visit. The house itself is authentic. Another site is the Martinez Hacienda. To appreciate that more fully you should read at least a bit about the appointment of Archbishop Lamy to Santa Fe and the tragic conflict between him and the local Catholic clergy, especially Father Martinez.
We always enjoy eating at Michael's Kitchen out near the post office, but there are many other possibilities.
A walk around the Plaza early in the morning is pleasant, and a drive up to the ski basin should be a part of any visit to Taos. The highest peak in New Mexico, Wheeler Peak, can be accessed by trails from the ski basin. A far easier trail would be up to Williams Lake at the base of the mountain. Another drive would be out to the Rio Grande Gorge high bridge.
We consider Taos a part of every visit to Santa Fe, and try to make the "High Road to Taos" every time. We visit Chimayo and try to eat at Ranchos de Chimayo. The Church at Chimayo and at Trampas are historic. The one an Chimayo is always open, but you will be lucky if you find the one at Trampas open.
Of course, I'm just hitting some high spots. We have made the "Enchanted Circle" starting at Taos and going around by Angel Fire and Red River a few times, but we've never made Red River the base of a stay.