Are you comfortable being "The Commuter Guy"? If so, you could host a meeting of people with any sort of tangential interest in bike commuting - answer common questions, have the major bike routes on a map, be prepared with handouts regarding common tips and myths.
Depending on the funds/size of the company, you could have one or two bikes available to borrow for lunch trips, lunch break errands.
I like the spare tools idea - inner tube, spare headlights, batteries, etc.
Is there already a weather protected and secure bike rack? If not, that is also a big commuter concern.
Do a commuter challenge for the roadies - they already bike in traffic.