Many things in writings by Toen and Vezzosi on HAG, see refs under Homotopical algebraic geometry
Toen: Segal topoi and stacks over Segal categories. File Toen web prepr msri.pdf. Analogous and in some sense equivalent to the notion of model topos, but some advantages. Includes a Giraud type statement characterizing Segal topoi among Segal cats. Notion of homotopy type of a Segal site, improving on the etale homotopy theory of schemes, and more generally on the theory of homotopy types of sites as defined by Artin and Mazur.
http://ncatlab.org/nlab/show/model+structure+on+SSet-enriched+presheaves this is probably relevant
nLab page on Model topos