Adam Green has nice concise writeup on how he created his first Google Map by hand. Interesting part is how it follows what seasoned programmers do when tackling something they haven't done before: start with something that works and then keep it working while modifying (aka hacking) and learning. In this case the end product is the RSS Alley map of companies and people working with RSS in the Boston area.
And speaking of maps how-to, Alex Barnett recently pointed-out this new 3-part tutorial on Ajax and Virtual Earth. The tutorial itself is a bit sparse but there is some working code for the .NET folks.