Most of that stuff is custom work being done for large service providers (for instance
/blog/archives/2007/05/comcast_zimbra_future_of_unified_messaging.html) but I've attached a pic of the example portal that's included for you to play with
To get you started:
Checkout your /opt/zimbra/mailboxd/webapps/zimbra/portals/
zmprov ma
user@domain.com zimbraFeaturePortalEnabled TRUE
zmprov ma
user@domain.com zimbraPortalName example
It can be applied to COS's as well - I would suggest working on a devel box or test account first of course

You can find some JSP tags (JavaServer Pages) in /opt/zimbra/mailboxd/zimbra/WEB-INF/tags/ (the 'mobile' folder contains some good examples)
We haven't yet rolled this out with a standard design or documentation - but you're more than welcome to write a community guide from what you can come up with on your own!
For things like voicemail & home portals, huge providers/organizations should contact their sales rep if they need to purchase professional services. Just please don't bog down the support staff with tickets about this - as this isn't a 'regular' feature yet.
