Building disconnected web based mapping application?

Would suggest Maps on a Stick

http://developmentseed.org/blog/2010/oct/02/maps-stick-version-2-released/

No more complex deployment process. Users can easily copy single-file SQLite tilesets to Maps on a Stick for viewing.

Adding online KML is as simple as inputting the address of the KML file and clicking ‘Add.’

Uploading KML consists of clicking ‘Upload KML’ and uploading it.

You can generate your own tiles with https://github.com/developmentseed/gdal2mb

See for Examples of the tools/maps http://afghanistanelectiondata.org/open

Here's the answer we chatted about.

OpenLayers + IIS (that you are running locally or on LAN) + Image as your base map.

And you can have different base maps at different zoom levels (all of them can be images) and that's answered in this question:

Switching baselayers as user zooms in to map in OpenLayers?

Re "You'll need a way to manage your maps locally. For this you'll need a map server ..."

No, not at all - other than the web server. We're using the 'URL/{z}/{x}/{y}.png' construct in our free, Open Source Computer-Aided-Dispatch application with a local tileset store (or as a dynamically-selected option, to any OSM repository).

Ours is in PHP, and I expect an ASP implementation to be quite similar since the tile interface is done by the JS library in user-land. Really sweet!

Our current implementation is GMaps-based, but we're moving rapidly to OSM, with one of the libraries discussed here. (See at www.ticketscad.org)