Google Apps for Domain and Google Account registered using that very same Google Apps for Domain mail account creates redundant services.

Gmailed Google Account
Google Apps for Domain 
Google Apps Google Account 
 Used by 
Comments 
 GMail
 Mail 
 Mail*
 
 Duplicate
 Calendar
 Calendar 
 Calendar**
 
 Duplicate
 Documents
 Documents 
 Documents**
 
 Duplicate
 Sites
 Sites 
 Sites**
 
 Duplicate
 Contacts
 Contacts 
 Contacts***
 Reader
 Duplicate
Have to be synced manually,
used to various services.
 Talk
 Talk 
 Talk***
 iGoogle
 Duplicate
 Tasks
 Tasks 
 Tasks***
 iGoogle, Calendar, Mail 
 Duplicate
 Maps
 
 Maps 
 
 
 Alerts
 
 Alerts 
 
 
 Picasa
  
 Picasa 
 
 
 Reader
 
 Reader 
 
 
 Shopping
 
 Shopping 
 
 
 iGoogle
 
 iGoogle 
 
 
 Finance
 
 Finance 
 
 
 Groups
 
 Groups 
 
 
 Web History
 
 Web History 
 
 
 YouTube
 
 YouTube 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Notebook
 
 
 
 Discontinued 

* Will change primary address on Google Account when created.

** Service subscription is optional and can be omitted,
   though clicking on link will not open Google Apps provided service and a new subscription is suggested.

*** Is created silently.



Links related to Google Apps and Google Account integration

Google Accounts: Google Apps vs. Google Accounts
http://www.google.com/support/accounts/bin/answer.py?hl=en&answer=81987
http://www.google.com/support/accounts/bin/answer.py?hl=en&answer=72709
http://www.google.com/support/forum/p/Google+Apps/thread?tid=3a574dd07bc77fe5&hl=en
http://www.google.com/support/forum/
http://www.google.com/support/a/
http://www.zoliblog.com/2008/01/20/google-apps-and-account-chaos-almost-fixed/
http://www.google.com/support/forum/p/Talk/thread?tid=7a1bcc31124ccdf9&hl=en