About a week about I got my car's power steering pump replaced, but since then it has constantly sounds like it revving, or rubbing fiercely against something...any idea what it could be?

I would recommend taking the vehicle back to the original repair facility. There's many potentials from something rubbing, the replacement part failing, air in the hydraulic system or an issue with the install depth of the power-steering pulley! Most repair shops are more than willing to correct any issue that's related to their work!