Jeff and Rich,

Great information!  I'd like to add a few comments, if I may.  What most companies tend to overlook are the small purchases, little office supplies and technology parts that they use every day.  Things like ink and toners for printers, staples, etc...  When you order these from "big-box" supply stores, you're going to pay premium pricing.  The same goes for your computers, printers, copiers, and fax machines.  You can get great deals on refurbs through the manufacturers, but you can get even better deals by looking at "end of life" distributors who pick these things up on expired leases, etc...  Partner with a procurement consultancy that can help you streamline your processes and find you the very best deals.  Move your purchasing from purchasing to "strategic sourcing."  You'll save unbelievable amounts of time and money in the process.