Foreign keys across databases?

[Jake Krohn]

I would like to use separate databases to group certain related tables 
to keep things clean, but I would also like to use foreign keys to 
enforce referential integrity between tables in different databases. I 
don't think this is possible. Am I right? And if so, am I reduced to 
using carefully chosen table names to keep things organized? What have 
others done in this situation?

Thanks,

Jake Krohn