Image maps are not something I would recommend doing by hand. Whenever I do image maps, I usually Macromedia Fireworks, but I am sure there is other freeware somewhere. It can be done by hand though if you want to. But it is tough, especially if the regions you want to be links are not perfect squares. The get infinitely harder when you introduce polygons. For a good bit of information on image maps, check out my extra credit homework I did involving image maps for a web programming class I took a couple of years ago. Here is the page:
http://elvis.rowan.edu/~mieskola/WebProgramming/region/assignment3.html
Make sure you view the source to check out how I defined the regions. Notice also how the the regions overlap, and how the browser handles it. If you have a more detailed questions, let me know.
PS: The web server the above page is hosted on is running slowly right now, so be patient!