A growing number of companies are encouraging workers to work from home. As the recession spirals downward and companies look to save money on real estate costs, what was once a cushy perk is now deemed a business necessity. Companies are selling the work-at-home concept to employees with a shiny new BlackBerry, free Internet and home office furniture. To encourage more of its workforce to become post-geographic, companies are offering free high-speed Internet access and gratis office fur