The 2x3 and 3x4 chessboard complexes (form a square grid of vertices and make a simplex for any set of vertices no two of which are in the same row or column) are a 6-cycle and a triangulated torus with 24 triangles, respectively. The 4x5 chessboard complex is only a pseudomanifold — each vertex has the 3x4 torus as its link, rather than a spherical link that a proper manifold would have — but if you delete its 20 vertices you get a bona-fide cusped hyperbolic 3-manifold, triangulated by 120 regular ideal tetrahedra. It sort of looks like the kind of manifold you might get as the complement of a 20-component link in Euclidean space. Is it a link complement? And if so, which link is it the complement of?

Edit: here are a couple of general references on chessboard complexes.

Ziegler, G. M. (1994). Shellability of chessboard complexes. Israel J. Math. 87: 97–110.

Björner, A.; Lovász, L.; Vrecica, S. T.; Zivaljevic, R. T. (1994). Chessboard complexes and matching complexes. J. London Math. Soc. 49: 25–39.

They also have important applications to the proof of colored Tverberg theorems in discrete geometry: see, e.g.

Pavle V. M. Blagojević, Benjamin Matschke, Günter M. Ziegler (2009). Optimal bounds for the colored Tverberg problem. arXiv:0910.4987.

regularideal tetrahedra. Do you know the symmetry group of the triangulation -- could this be something as simple as a 120-sheet cover of the Gieseking manifold? – Ryan Budney Aug 27 '10 at 8:08