Here are five extremely useful computing resources that are free of charge for small business users--unlike some "free" services you might see that are only for home users. These choices have few if any restrictions, and are established services unlikely to shut up shop anytime soon.

1. Google Apps For Business

If your organization has under 50 employees, then (formerly called Google Apps for Domains) is for you. It offers free e-mail under the umbrella of your own organization's domain name (You can pay Google $10 to reserve a domain name, if you don't already have one). You can also have your own private Google Docs system along with your own Google Calendar system.

In use, the e-mail system looks and feels just like regular Gmail, except that your own organization's e-mail addresses are used rather than a Gmail one (such as, bob.smith@yourdomain.com, rather than something like bob.smith1964@gmail.com). is that the e-mail address book is shared automatically amongst your users.

It's all hosted on Google's computers, so you won't need your own mail server computer. You'll benefit from almost zero configuration and maintenance, plus a promised 99.9 percent uptime guarantee. Put simply, . The spam filtering is the same excellent system as Gmail, which is to say your employees just won't be bothered by anything dodgy.