I'm not easily sold on software enhancements other than the general editing but when I want to have some fun, like Twirling (yeah I said Twirling) then Topaz Labs is my favourite for editing features.
While Twirling might not seem like a photographic quality, it does help to have a decent photo to start with and once you start with Topaz Clarity, Simplify, Glow etc you start creating beautiful abstract art.
My personal favourites are Clarity (for its non-destructive sharpening qualities), Remask (for detailed masking of areas) and Glow (beautiful ethereal results).
Topaz works with Lightroom and Photoshop as a plugin or can work through an standalone program called PhotoFXLab.
The PhotoFXLab allows you to apply multiple effects to one photo which is a plus when working in Lightroom and you want to add more than one effect.
Below are some examples from just some of the software from the Topaz Collection. All was done in Lightroom 4.
From the top go to the left: Original photo, Simplify, Lens Effects
From bottom to left: Restyle, Mix (Simplify, Lens Effects and Star Effects), Glow
You are also welcome to give the software a trial run for 30 days. Read the requirements for Glow, Impressions and Textures.
Take a look at their website: Topaz Labs
Topaz Labs also features videos to help you get started with each of the different effects.