I have a domain controlled with google-apps. Now I want blog.mydomain.com to be a wordpress blog. How do I do that? 
Integrate google apps with wordpress
google apps;wordpress
I think you have 2 options both of which require you to use Google-apps support for mapping your domain to a google appengine application.You can use Google Appengine to run Wordpress (it's a bit of an advanced technique) with your Google-apps and assign blog.mydomain.com to your google appengine application.This blog describes the modifications you need to make to wordpress to run on Google's Datastore and to run PHP through the Java runtime:Quercus on Google App EngineYou can see it running as Java Google Appengine application:http://wordpress-on-quercus.appspot.com/wordpress-2.7.1/Ever since Google App Engine (GAE)  supported Java, it has opened a slew  of other languages that GAE indirectly  and unofficially supports. PHP is one  of them through Quercus, our 100% Java  clean-room implementation of the PHP  language.I set to gain insight on this  interesting question by getting  Wordpress running on GAE. Since  Wordpress already runs on Resin with  Quercus, all I needed to do was  convert the MySQL queries to instead  use the App Engines subset of JPA. In  the end, it took about a week of  uneventful work to get enough of  Wordpress running so we could demo it  at Google I/O.at Google I/O.Another alternative might be to use Google Appengine as a reverse proxy, mirroring your wordpress hosted site (Google appengine would allow you to handle massive surges in traffic and comes with huge free quotas).bs2grproxy - A small app runs on Google App Engine as a reverse proxy to a specific site, completely transparent to clients