I'm lucky that my husband used to style hair, so he knows how to color my hair for me when my gray roots start to show. He mixes Salon Care 20 Volume Creme Developer with my hair color, and it does a great job of giving me a very professional-looking dye job. Of course, my hair color is pretty good stuff, so that helps (I did a review on it separately).
This creme developer has no detectable fragrance, and the ingredients are water, hydrogen peroxide, cetearyl alcohol, ceteareth-20, stearic acid, cetyl alcohol and phosphoric acid. I don't know what half of these things are, but I do know that this product, along with my hair color, does a nice job. A 32 fl oz bottle lasts quite a while, and the price is not bad at $4.69, since you get quite a few uses out of it. It is available at Sally's Beauty Supply, and I'm sure that other beauty supply outlets would most likely carry it as well.
My husband told me that this type of developer is more gentle on the hair than a developer with a higher strength of peroxide (such as 30 versus this product at 20). I'm all for anything that is not so harsh on my hair.
Salon Care 20 Volume Creme Developer seems to be doing a good job with my hair color. My husband and I will continue to use it.
Update On Jul 13, 2010: Every time my husband dyes my hair for me, he uses this developer. My hair color always comes out beautiful. Of course, I'm sure my husband's talents have something to do with that, but the developer helps the results to come out really well.