Plone (http://plone.org) is a CMS that you can use to setup a portal or intranet with features similar as Google Docs. In fact, there's a module that let you write math using latex format: http://plone.org/products/latex-math-image
Plone is not only open source, but has a strong support from its community as any successful FLOSS project and also professional provided by a network of business and people in more than 60 countries as you can check in http://plone.net/
r0ver writes: "Open source experts from the public sector, SME and Plone community participated in the first Plone e-government international workshop. After two days of intense work the group decided to merge into 1 common project 3 e-government initiatives: CommunesPlone (Belgium, France), PloneGov.ch (Switzerland) and UdalPlone (Basque Country, Spain). The new project, based on the open source Content Management System Plone, will be named PloneGov.org. It now reaches over 40 local governments and 2 regions in 5 countries."