Personally I would go for SOGo as a web frontend for email. I like the layout and how it works. Besides that I think Webtop 4 is a java resource hog. Although I rarely use the web client. I mostly use mail through thunderbird.
Wordpress is a CMS (=Content Management System) which is available via NetForge repository: http://dev.nethserver.org/projects/nethforge/wiki/Nethserver-wordpress
You could argue what CMS is most usefull. I have used a few different types: Drupal, CMSMS and Plone. Depending on what your aim is, choose any CMS you want. It might need some fiddling with LDAP settings to get LDAP authentication working.
If you ask for Sharepoint and Alfresco, IMO those are DMS's (Document Management Systems) or Collaboration Systems. Anyway, I would stay far away from Alfresco since it is java based. I just don't like that, but that is my personal opinion. For a DMS I would like to see SeedDMS