Very Good for the Price

You can spend much more on plugins like onOne or Topaz. They will probably do more for you but if you want to get started with something at a more reasonable price, you could do a lot worse than Intensify. They also sell a pro version on their website that will work as a plugin for programs such as Lightroom and CSx. This has provided me with some very useful tools when working with an image. Given it supports layers, this is an added bonus.

5L6speed about Intensify, v1.0.0