Google is giving their workers a home office allowance of $1000. Not bad for a start, as the companies are saving a huge money when they start to reduce their property rental costs. And these are not one time fees, these reductions will have an effect every month!
Another quite interesting approach with working in home offices on a regular basis is implemented by Automattic, the company behind WordPress.
Their work force is completely distributed all over the world. The employees are also getting a one time home office allowance to setup their environment as they like and feel comfortable.
Due to the worldwide distribution they have a huge problem to define the „correct“ salary for each employee. You have to take a lot of constraints into account.