I gave a talk at the State of the Map conference at Limerick and some people were interested in CartoType's CTM1 data format, mainly because it is very compact (UK data = 37Mb; Germany = 50Mb). I have documented it and made it freely available with an attribution license: see http://www.cartotype.com/cartotype_map_data_format_type_1.html.
Discussion
Comment from Harry Wood on 16 July 2008 at 12:07
I put a brief description of CartType (and link) on the a new wiki page, just as a placeholder really to help people find it.