Paulie,
I don't know if they still do this or not, but either Performance or Nashbar used to print a BCD determiner in their catalog. If you've got some catalogs hanging around, you can flip to the crankset pages and look for the BCD tool, or whatever they call it.
The typical BCDs are 144, 130, 110, 74--the ones my experience is limited to--but I know there are others (such as the old Campy 151 and some newer ones.
You can probably find this stuff on-line, too, though I don't know where. (Sheldon's, maybe? Or The Third Hand?)
Good luck with the chainrings!
nath dresser
spring green, wi