Outlook Users
Here are some tips for making the switch from Microsoft Outlook® to Google Apps. 
Switching from Microsoft Outlook®
Going Google Transition Guide

Quickly learn to accomplish some of the same tasks in Gmail that you're used to doing in Outlook.

Print this guide out and keep it handy as you begin using GMail, GCal and Chrome.
What's not available in GmailSee features you might be used to in Outlook mail that aren't in Gmail.
Switching form Microsoft Outlook®: Gmail and Calendar Self-paced training (short clips - 1 hour total) A comprehensive introduction to switching from Microsoft Outlook® to Google Apps. Covers threaded email conversations, contacts, labels, mail filters, calendar events, syncing events from Outlook, and more.