Wow, thats a big network you are planning to put together.
You need to follow a hierarchical design with Core, Distribution and Access layers. You can also use a collapsed core where Core and Distribution layers merge and the Core does layer 3 routing.
At the access layer, users (Pcs or ip phones - if using ip telephony) all go into workstation switches like Cisco 2950, Cisco 3750 or Cisco 3560 with or without inline power at the wiring closet level. For higher port density you could stack multiple 3750s (with separate stack cable). You can stack upto 9 switches. Or if you prefer a chassis based switch for higher port density, at the wiring closet level you can use a Cisco 4506 or Cisco 4507.
All the wiring closet switches are aggreagated by multiple core switches (which will do layer 3 routing for all the vlans in your network). You should be looking at using a Catalyst 6509 or 6513 series or even a Catalyst 4510 series. Using two switches for redundancy is a very good idea.
You will need to get fiber modules for the core switches for the fiber runs coming in from other buildings. Most of these modules are empty line cards which have to be filled with a GBIC (Long haul or short haul).
Note that 2950, 3750, 3560 are typically used at wiring closets. 4500, 6500 series are typically used for higher port densities and used either in Core or distribution layer.
HTH
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus