Google-apps – Google Apps – possible to transition only some users

This used to be available, but has been discontinued:

Note: The previous Start Page service was a syndicated version of iGoogle; it allows you to set up a dynamic homepage (one start page layout per domain) for your users that brings together your content, Google services, and the best of the web. Starting on 3 December 2008, the Start Page is no longer included for new organizations that sign up for Google Apps.

(From: http://www.google.com/support/a/bin/answer.py?hl=en&answer=46798)

However, you can now make your own via Google Sites:

As a Google Apps administrator, you can create a Start Page for your users, using the Google Sites Start Page template. This page is your users' homepage, on which they can access their Google services and other content -- such as interactive gadgets and RSS feeds -- when they log in to their Google Apps accounts.their Google Apps accounts.

(From the tutorial: http://www.google.com/support/a/bin/answer.py?answer=179916

We needed to setup a distribution list where there were many aliases but they all were delivered to the same users. The best approach we found was creating a fake user account, setting up aliases on that account, forwarding the email to a real group, and using the group membership function to setup the distribution list. Works reasonably well, but having aliases for a group would be better.

Looks like you can also nest groups within groups. There is at least one help topic that recommends this approach. The above mentioned approach does give a few other features however, such as vacation responders and the ability to backup mailing list email using POP/IMAP.