I need some help!

I work for an organization with a little over 300 employees housed in 2 large buildings. There have been a lot of complaints regarding internal communications (specifically, the lack thereof).

Budget constraints prohibit the hiring of a new person to work on internal staff communications, yet something is needed to keep everyone apprised of events that are going on, projects and programs people are working towards, etc.

Does anyone work for a company, association, government agency that employs a simple notification system? What do you do to keep everyone informed? How is information collected? How is it distributed? Does anyone know of any online tools that might give me ideas?

All suggestions are greatly appreciated. Everything I've come up with is too time-consuming.