Okay, so this post is from six months ago, but I thought I would add some info here for people who are confused about the whole API key/MD5 fingerprint business. It took me a while to figure out, so I assume others have had trouble with it too (unless I'm just that dull).
These directions are for Windows XP, but I imagine it is similar for other versions of Windows. It appears Mac and Linux users have an easier time with this so I won't address them.
So in order to use mapviews in your Android apps, Google wants to check in with them so you can sign off on an Android Maps APIs Terms Of Service agreement. I think they don't want you to make any turn-by-turn GPS apps to compete with theirs or something. I didn't really read it. Oops.
So go to http://code.google.com/android/maps-api-signup.html and check it out. They want you to check the "I have read and agree with the terms and conditions" box and enter your certificate's MD5 fingerprint. Wtf is that, you might say. I don't know, but just do what I say and your Android app doesn't get hurt.
Go to Start>Run and type cmd to open up a command prompt. You need to navigate to the directory with the keytool.exe file, which might be in a slightly different place depending on which version JDK you have installed. Mine is in C:\Program Files\Java\jdk1.6.0_21\bin
but try browsing to the Java folder and see what version you have and change the path accordingly.
After navigating to C:\Program Files\Java\<"your JDK version here">\bin in the command prompt, type
keytool -list -keystore "C:/Documents and Settings/<"your user name here">/.android/debug.keystore"
with the quotes. Of course <"your user name here"> would be your own Windows username.
(If you are having trouble finding this path and you are using Eclipse, you can check Window>preferences>Android>Build and check out the "Default Debug keystore")
Press enter and it will prompt you for a password. Just press enter. And voila, at the bottom is your MD5 fingerprint. Type your fingerprint into the text box at the Android Maps API Signup page and hit Generate API Key.
And there's your key in all its glory, with a handy sample xml layout with your key entered for you to copy and paste.