I got a nandroid backup of a stock android froyo firmware. The device (GT-I9003, Galaxy SL) is now running cyanogenmod 9. how can i transfer the contacts (and sms/mms optionally) from the backup to the running system?
If you had contact sync enabled and you added the account on this rom too your contacts should appear. If they don't, try Titanium Backup Pro. It's a terrific backup solution and it's pro version allows you to restore individual items from CWM backups.
It costs more than your average app but it's super well worth it.