I may be mistaken, but I don't think brush cleaning is high on the list of fun things to do for most people. But it is an important thing to do and the easier it is, the more enjoyable it will be for both you and your brushes. I have been using Brush With Success from Mecca Cosmetica for two years and I recently had to replace it. It is a little exxy at $22 for 125 mls but it lasts for a long time and gets the job done. No harm is caused to your brushes either because the brush cleanser is gentle and effective.
The directions are very simple and the ingredient list is nice and short. Mecca also does not do animal testing.
How often do you clean your brushes? How do you do it?