I would like to use Rite of Consumption by sacrificing a creature that is using equipment (e.g. that has a +1/+2 bonus). Is the creature's power then increased by the equipment effect, and thus available for the Rite of Consumption?
Yes - spells like Rite of Consumption check the last known information on the most recent public zone (in this case, the battlefield, where the equipment will be attached when that power is checked).
From the comprehensive rules: