Based on what we're seeing in Buildatour.com tours, a large number of agents are using some type of photo editing software. There are numerous photo editing software packages available ranging from freeware to the ultimate, Photoshop Creative Suite 4 (CS4). Photoshop CS4 Extended full version is priced at $2,499 online at Adobe's Online Store.
http://store1.adobe.com/cfusion/store/index.cfm?

We have been using Corel's Paint Shop Pro Ultimate Photo X2 for quite a while now. For the money, we think it's a good options for agents that want to get a little more out of their images after they're shot.
http://www.corel.com/servlet/Satell...4951547051

Paint Shop Pro X2 offers extensive features, and the price is now down to $79.99 (Full Version).

Adobe's answer to Paint Shop Pro, or vice versa, is Photoshop Elements (Full Version from $99.99).
http://www.adobe.com/products/photoshopelwin

What editing software do you use? Do you have any recommendations on purchasing or using photo editing software?

I use Photoshop Elements and very happy with it.
Google offers a free photo editing package called Picasa, not as robust but it is free and for someone who is not used to using photo editing software it might be an inexpensive way to get their feet wet before purchasing something more robust.
Here is the link ... http://www.picasa.google.com