If you just want to add your home (for example) to a Google map to show on your own site, all you have to do is to start a new map in My Places, and drop an icon at the relevant point. You can add whatever description you like to the icon, and your visitors will see that description when they hover over it. For more information about how to do this, see http://www.hexcentral.com/articles/maps-tutorial-1.htm.
This won't cost you anything, but your icon will not be seen by the general public. It will only be visible to people to whom you give a link to the map.
You can embed the map in your own website. The map, including the icon, will then be visible to your site visitors, who will be able to zoom, pan and scroll the map, and do all the other things they can do in Google Maps. Again, this won't cost you anything. For more information, see http://www.hexcentral.com/articles/maps-tutorial-2.htm.
The same map can contain multiple icons (one for your home, and one for your office, for example). You can choose from any of Google's icons, or create your own.
There's a lot more you can do with My Places, but the above should give you a good start.