Office packages today have a new trend, it’s not necessary for a company to purchase a desktop-based office package like Microsoft Office in order to get started. The new trend is based on cloud web applications, which enable users to launch office applications through their browsers. This trend provides a cost effective, fast, and anywhere-access solution for employees. In addition, for some services, it supports collaboration, which means that many employees can work together within the same document without conflicts.
Examples to this service is Office 365 , Google Apps and Zoho.
This article from ReadWrite provides good comparison between such services including pricing.