I did implement a web content managment system using Joomla content managment recently. There are lots of OOBT functionality for news/press relase integrated into the system. You can install the Joomla CMS on windows and Linux. Its a LAMP based CMS implementation. Its very easy to edit content using the built in WYUSWYG editor. The Joomla system does not a any good workflow engine as TeamSite. All the content static or dynamic and is stored in the MySql database, it uses templates to this render the site at run time. You can find more information on the web site Joomla Content Managment System.
Unfortunately, I can't recommend joomla CMS engine at all.It is fancy and includes WYSWYG editor. However, I don't think it will be simple for your end users. We did a simple web site based on joomla.org just a few weeks ago and encountered some bugs (content files get locked, 'cancel' option is not well designed, upload/manage images framework is not simple nor intuitive, etc.). Quite often, it is not possible to find what you are looking for.This is based on a real experience. Others might have opposing positions.
>> Budget is tightWhat is the budget? ;-)WYPIWYG (What you pay is what you get)