The conversion is far from perfect, but will handle most major html tags besides tables. img src attributes will point to their absolute paths on google sites.

Liberate your sites from google using Google Sites Liberation

Here's what it looks like for a google apps domain:

note: if you have two-factor authentication, you'll probably have to generate a password for this

• java 1.7
• maven

1. Make sure your environment's jvm is 1.7

    # verify the version
    java -version
    # set the JAVA_HOME to the appropriate path (like this on osx)
    export JAVA_HOME=/Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home
   

2. Run the conversion

    export MAVEN_OPTS=-Dfile.encoding=UTF-8
    mvn compile
    mvn exec:java -Dexec.mainClass="jon.Convert" -Dexec.args="/path/to/exported/sites/ /path/to/markdown/destination"
   

3. Use gollum to host your new wiki!