I use both Gmail and Microsoft Outlook on a day to day basis, making use of email, contacts and calendar to manage my day to day life. However, managing multiple calendar entries and contacts can be quite a hassle.
Google Contacts Outlook Synchronizer is a handy freeware that synchronizes the contacts between Outlook and your regular Gmail account. This app also supports contact synchronization for Google Apps account.
Once you install the software, choose the direction in which the synchronization should happen. You might want to choose a higher Synchronization interval, as you hardly keep editing contacts every 5 minutes, 6 to 12 hours interval should be good enough.