Java's documentation on this tool is bad. I had a heck of a time figuring it out and created a walkthrough for myself in case I ever needed to do it again. It makes sense to me, hopefully it makes sense to the world.
I use Java version 1.6 and assume this should work for whatever version you have but you'll just have to change the version numbers in your file folders.
1) open command prompt
2) change directories to this directoy: C:\Program Files\Java\jdk1.6.0_26\bin
3) copy paste this (obviously change Dude with your curent windows username)
keytool.exe -list -alias androiddebugkey -keystore "C:\Users\Dude\.android\debug.keystore" -storepass android -keypass android
4) MD5 will be displayed in this pattern where X can be a number or letter:
XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:
5) Go here: http://code.google. com/android/maps-api-signup.html
6) follow steps and your apikey will be generated will look something like this:
(fyi I just mashed a bunch of keys to create the string shown below)
From Google Web API Key Tool
Your key is:
93dn23o812dsm19021087ry2f823o8fn3f0vkTL
This key is good for all apps signed with your certificate whose fingerprint is:
XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:
Here is an example xml layout to get you started on your way to systemic mapping glory:
<com.google.android.maps.MapView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:apiKey="93dn23o812dsm19021087ry2f823o8fn3f0vkTL"
/>