I've bought/registered/verified a domain with Google Apps, setup an email etc. so far so good. Everything works.
How to now setup/host a small static page (plain HTML saying "Soon! :)" or something), on that domain using Google Apps?
Since Google Apps is now setup, you'll want to activate Google Sites on the domain. You can associate a specific URL with your Google Sites location (such as
Google App Engine (GAE) was designed to serve dynamic pages, but it is possible to set it up to serve static content:
Note these instructions are for GAE 1.4.3; some details may have changed with the new 1.5.0 version.
Alternatively, for a temporary "coming soon" page, it may be sufficient to simply start with the default app.yaml and configure the custom (404) error responses to serve the "coming soon" page. Make sure the app's root index page is not handled/cannot be found.