Applications of association schemes to complexity theory and other TCS
One application that I know of is the connection between combinatorial designs (which are related to associative schemes) and coding theory. Delsarte's program in particular has lead to some interesting LP based bounds for codes. I don't know much about these but I remember that Alex Samorodnitsky has worked on these connections (for example, this, this, this and this). Perhaps some expert can shed more light on this.