I just found one great tutorial for rendering osm in custom projection.
The tutorial is locate at http://www.justobjects.org/blog/?p=45
It covers import raw data to PostGIS. and setting up Mapnik osm.xml with right projections.
Last but not least, how to setting up tilecache with mapnik.
then you can use seed tool from tilecache to cache all the layer in your own projections.
or you can try to rewrite seed tool from mapnik. but the tool is default for projection 4326. you have to modify the script.
There is some differences between these tools, the tool from mapnik or osm community is store all tiles in standard XYZ folders.
so you can render the cache via OL xyz layer.
The cache from Tilecache is stored in tilecache own name convention.The cache is not store in standard XYZ tiles.
You cannot render tilecache cache file viw OL default XYZ layer. At least I tried and failed.
For more details, better check Just' tutorials.
Xiaoyu Guan (Sam)