These were the default Apps displayed when I activated my Google Apps premier account in my developer edition of Salesforce. I suspect they differ between editions:

Configurable
Google Docs to Salesforce salesforce.com
Google Docs Tab salesforce.com
Gmail to Salesforce salesforce.com
Gmail Buttons and Links salesforce.com
Google Talk Sidebar Component salesforce.com

Installable
Appirio CRM Dashboards for Salesforce & Google Apps Appirio
Appirio Calendar Sync for Salesforce and Google Apps Appirio
Appirio Campaign Timelines for Salesforce & Google Apps Appirio
Appirio Contact Sync for Salesforce & Google Apps Appirio
Appirio Search for Salesforce & Google Apps Appirio
Arcot SSO and Strong Authentication for Salesforce and Google Apps Arcot Systems, Inc.
Astadia Quoting for Google Docs Astadia, Inc.
Astadia Report Collaboration for Google Spreadsheets Astadia, Inc.
Gmail to Salesforce Browser Button for Firefox Salesforce Labs
myOneLogin User Manager TriCipher, Inc.