XDA member dewang just came out with a small app to allow you to group your contacts in many different categories (a few extra ones aside from the ones offered as standard by Android. Moreover, the app allows you to place folders/widgets in your home screen for easy access. Nifty, small, and best of all, free. This app can certainly be improved as it is its first release, so make sure that you download it and leave some feedback for the dev as well.
Laminated display sub-group support
Send group e-mail
Send group SMS
Set group ringtone
Desktop shortcut to the group
Whether to display the Contacts icon in the Options
Contact Birthday show
Contact organization view (support to send group messages to the organization)
I hope you like it.
You can find more information in the application thread._________