How can I create one markerset by category?

There is 2 solutions for this :

1 - Create one markerset for each category:

• Create one markerset
• Set a custom icon, a name based on the category, and select the needed category (in the last tab of markerset editor)
• Do this for each category and attach each markerset to the same map
• When you load the map you will see all markers (of all markersets)
• In addition if you set the [sidelists] controler in the map template, the user can select what markerset to display

2 - Display automaticaly the entries:

• Create one markerset
• Set this markerset to use each entries of each categories, and set the Auto cat to yes
• When you load the map you will see all markers (of all categories)
• Install the free Geocode Factory module, and publish it on the directory pages
• Then when you browse the categories, the map (in the module) will show only the current category (and child), entries.