I don't have much yet, but there are now links on my website for some keys to Malacothamnus:
http://www.keiriosity.com/malacothamnus.html

Also, Tom Chester and I just put together an illustrated guide to the Malacothamnus of San Diego, Riverside and Orange Counties which you can view here:
http://tchester.org/plants/analysis/malacothamnus/enigmaticus.html

Sample image from the guide.