I've now got a page http://hcmc.uvic.ca/grs/map/ that can dynamically create and load a layer from a KML file. Right now the data is all static (hand-made KML files), but the tech (all JS)should work work in any environment.

I've been trying to get this working with a Google base layer, but most commercial providers use a Spherical Mercator projection, which uses X/Y coordinates (in metres for the most part); my system uses lat/lon. The maps that I'm caching (using GeoWebCache) are EPSG:4326 - read NOT Spherical Mercator, meaning that dots on my vector layer representing cities are in the ocean when one switches to a Google layer. While this can be overcome by not using a Google layer, I cannot achieve the same resolution with my sources so if you stick with My BMNG or Modis layer, the image becomes unusable very quickly. It is apparently possible to have openlayers do the math on the fly, but I'm still trying to figure it out. Docs here: http://docs.openlayers.org/library/spherical_mercator.html