The basic Google Apps suite is a familiar set of online productivity applications: a calendar, an office suite, and a collaborative website builder. But what really makes Google Apps for Business a worthwhile investment is that it's a platform for a host of other business applications from other vendors. In the Google Apps Marketplace, you can find third-party document management tools, CRM and marketing tools, accounting, project management, and much more. In fact, you could (and some folks do) pretty much run an entire business with software built on the Google Apps platform.

Google Apps for Business costs $50 per user account per year. Expect to pay a bit more, however, for most add-on services or expert support available from the Apps Marketplace.