The following videos are produced by Google to introduce the various Google Apps features.

Google Mail:
    Introduction to Google Mail
    Introduction to Voice and Video Chat
    Introduction to Sending Instant Messages
    Good Explanation about Threaded Messages in Google Mail

Google Calendar:
    Introduction to Sharing Your Calendar
    Scheduling Meetings in Google Calendar
    Changing Calendar Views (Day, Week, Month)
    Creating an Event in Google Calendar
    Copying an Event in Google Calendar
    Create an All Day Event in Google Calendar

Google Mail Videos:
 

Introduction to Google Mail

    

Introduction to Voice and Video Chat
 

Introduction to Sending Instant Messages

    

Threaded Messages in Google Mail
     
 Google Calendar Videos:    
 

Introduction to Sharing Your Calendar

    

Scheduling Meetings in Google Calendar
 

Changing Calendar Views

  

Creating an Event in Google Calendar

 

Copying an Event in Google Calendar

  

Create an All Day Event in Google Calendar