I am happy to do that, thanks for asking.
IMAP Email - Email accessible as an email client. In other words being able to access multiple email accounts from the same login, without needing to log out and back in again to view each one (which is how webmail works).
Address Book - Contact lists that are available to any user that has a groupware account. Contacts are also available to multiple email accounts.
Calendar - integrated into a groupware package would be nice, though I know that WebCalendar is a good application and available as a One-Click installation.
Tasks - a way to keep task lists accessible to all users in the groupware account. This may be part of WebCalendar also, I haven't used WebCalendar for years so I'm not familiar with the most current version.
Applications that I am looking at and considering for installation:
Feng Office - http://www.fengoffice.com/web/opensource/
EGroupware - http://www.egroupware.org/community_edition
EPESI - http://www.epe.si/
Feng Office looks closest to what I need, I've used EGroupware prior to my move to DreamHost so it's familiar, and EPESI looks promising.
Just found that Horde (popular webmail app) has a groupware application as well - http://www.horde.org/apps/groupware
Kolab looks really good too (http://kolab.org/) but both Kolab and Horde need to be installed by admin at DreamHost and are not for a shared host installation (that I can tell or want to fuss with).