Two glaring weaknesses I've always seen in DNN regarding communication/interaction between members.  I'd love to see these added to the core. 

ListServ - Right now, members can only communicate/collaborate by logging in and participating in a forum.  Need to have some sort of ListServ capability where members can can communicate and participate in forums by simple email.  Conceptually, have a members@mydnnsite.com mailbox set up somewhere that members send email to from their favorite email client.  DNN accesses that mailbox (via POP3 transaction?), pulls in the messages and then redistributes via email to people in appropriate roles.  List membership is associated with a particular mail address (members@mydnnsite.com goes out to all Registered Users, board@mydnnsite.com goes out to members of a Role called "Board of Directors", etc).  Also have DNN post messages to the forums via this email path so people don't have to log in and navigate throught the forum.  This is the way the YahooGroups message forums work.  When accessing the mailbox, DNN rejects any message that didn't originate from the email address of an authorized user.

Member Directory - why do we have to write custom modules or create our own SQL queries and associated XML or HTML to create a Registered User-accessible membership directory.  I want my members to be able to easily lookup contact, bio and picture info on other members who have opted to make those profile properties public.

we have such a module ... called phonebookpro
 http://www.effority.net/MainModules/PhonebookProAJAX/tabid/65/Default.aspx 

we are going to release a new / enhanced version soon ... for free i think ;)

I'll check it out.  Thanks.