Seek out and evaluate new sites for network nodes. Take into account coverage mapping, costs involved, special restrictions, sustainability, ham population density, etc.
Useful links: Map of zip codes N4MC's Ham Locator Ham Creeper Puget Sound repeater sites
Use these two together to identify hams which are high up enough to be useful to the project. Perhaps they'd be willing to host nodes for free?
Nodeshot: A good node mapping tool, overlay for google maps
PolyPlot: A Google Earth extension that allows for drawing of circles and other shapes
Google Earth plugin for FCC tower database