I just thought of the things we need to document about special database configurations we've made to let tests pass. Sorry if it is not the right place for this king of stuff.
Here is what I can think of now:
sybase: number of user connections=200; max memory=65536; #Allow_DDL_in_Transactions
DB2 8.2: ASLHEAPSZ set from 15 to 50
MSSQL 2k5 with jtds: ALTER DATABASE <your db> SET ALLOW_SNAPSHOT_ISOLATION ON; ALTER DATABASE <your db> SET READ_COMMITTED_SNAPSHOT ON;
mysql: use innodb

I don't think copy and paste to the docs will be a good idea - I just point things out.