Here are some tips if you’ve recently switched over to Google Apps:

Set Up Outlook to Connect to Google Apps via POP:

Here is the directions on how to set up Outlook if you want to continue to use it:
http://mail.google.com/support/bin/answer.py?hl=en&ctx=mail&answer=12103

Set Up Outlook to Connect to Google Apps via IMAP:

Here is the directions on how to set up Outlook if you want to continue to use it:
http://mail.google.com/support/bin/answer.py?hl=en&ctx=mail&answer=75726

Get your Old Emails into your New Google Apps Setup:

And this is the program that you can install on any computer that has old emails in Outlook that you’d like to upload to the new Google Apps setup:
http://mail.google.com/mail/help/email_uploader.html

Setting up Mobile Devices:

Blackberry:

Setting up the Gmail app on a Blackberry:
http://www.google.com/mobile/blackberry/mail.html

Or you may want to just use your Blackberry’s email program and follow these settings (that above option is probably the better approach though):
https://mail.google.com/support/bin/answer.py?answer=78882

iPhone:

http://www.google.com/mobile/apple/

Also, check out Google Sync for syncing up your calendars and contacts.