The downside to our myPolkApps setup here is that it doesn't communicate well with Active Directory (yet) so all the distribution groups we have and our polk-fl address book is not synched with Google Apps. This makes sharing items with many people a daunting task. One thing you can do to help is to import contacts via a CSV file (a certain type of spreadsheet that can be made in Excel). It needs to be in a certain format. The following links will explain how to do it.
Importing CSV files
Creating or Editing CSV Files