At one point, I remember being excited by seeing the website Encyclopedia of Combinatorial Structures as an extension of Sloane's Online Integer Sequence Database site. Unfortunately, the site (ECS) has already become largely defunct.
I would very much like to see a searchable database of combinatorial objects online -- ideally, not just as a site with pictures or counts of these structures, but a database with downloadable files in SOME format containing usable, interpretable copies of these enumerated sets (a la the ARG database for labeled and unlabeled graphs.)
Broadly requested, does anyone know of such a site or sites? In particular, I am asking as part of a search for lists of polyominos stored as matrices (rather than just displayed as a picture), but I'd be curious if such an encyclopaedic site (or sites) exists -- and if not in general, then I would love to be pointed to a few databases of specialized combinatorial structures.