Just wondering. Oh, and not counting template mods, as otherwise people would be able to list hundreds.
I have 28 add on products with 4 of them disabled for various reasons. Mainly major modifications with plenty of features and that some members are dependant on.
I normally have between 4 and 5 mods installed on my forums at any given time. The only exception being my Fable Forum which has vBSEO and Photopost vBGallery installed, too.