What are the widths of Shimano 8, 9, and 10 speed cassettes?
I think these may be what you're looking for. FYI, a lot of this information is available with a little searching. Depending on what exactly you are looking for, you might want to look up a document for a specific cassette as the numbers might be slightly different.

Spacer widths (From Shimano tech docs)


8  Spd: 3.00mm
9  Spd: 2.56mm
10 Spd: 2.35mm (1.0mm for lower spacer)


Cog/Tooth Width (From Sheldon Brown)


8  Spd: 1.8mm
9  Spd: 1.78mm
10 Spd: 1.6mm


Chain widths (From wikipedia)*


8 speed - 7.1mm (all brands)
9 speed - 6.6 to 6.8mm (all brands)
10 speed - 6.2mm (Shimano, Campagnolo)
10 speed(Narrow, Direction) - 5.88mm (Shimano CN-5700,CN-6700,CN-7900)


*These chain widths are the standard widths, which I assume are recommended. I wouldn't go wider, but a narrower chain will probably work as some chains are cross-compatible.