MapBlast is a web based map and directions provider.
Here is some information from EricJohanson on how the MapBlast URL scheme works.
It's pretty easy to get it to plot upto about 25-50 'spots'. Much more than that, and you run into limitations in HTTP.
Here is the basic format:
http://www.mapblast.com/gif?&CT=47.6638000:-122.3783833:20000:&IC=47.6730000:-122.3983833:100:home&FAM=myblast&W=6000&H=3500
The CT is the center of the image. The 20000 is the zoom level; not quite sure how it works.
Each spot you can represent with a IC=; the format is as follows:
- IC=lat:long:icon_number:name
Finally, the W & H is the width & height of the image you want.
I'm sure there are more tricks you can do, but this is about all I know so far.
If you figure out what the 'zoom' level represents, it would be very helpfull.