The EEOC has issued new guidelines on religious discrimination in the workplace, after receiving the highest number of complaints ever in this area in fiscal year 2007 (it's doubled since 1992).
Accommodating religious diversity in the workplace means more than deciding if a Christmas tree or Menorah should be displayed in the reception area.
There are any number of federal and state laws that may govern this issue, including the Civil Rights Act of 1964.
While employers must assist with all reasonable requests, they are less obligated to leap major hurdles to accommodate a religious request than they would be for a employee with disabilities - but it still requires an acute knowledge of what's acceptable or not.
Make sure to work with your human resources consultant or employment attorney when any matter such as this arises. And read this excellent article from Jennifer Nycz-Conner in the Washington Business Journal.