I’ve currently got a Google Map showing successfully and it looks like this:

I want it to show with the info window showing by default, like this example:

I read this page: http://code.google.com/apis/maps/documentation/javascript/overlays.html#InfoWindows but that seemed to only explain how to make an info window with your own custom content. I just want to show the info like the example above where you see on many sites.
You can use the Places API:
http://code.google.com/apis/maps/documentation/places/
Or the Places Library (part of the Google Maps JS API):
http://code.google.com/apis/maps/documentation/javascript/places.html
You’ll parse the response in JS and then set the content of the infowindow as needed. Note that scraping content from business listings (at least on Google’s domains) to fill your infowindows is against the terms of service.
Here is a basic example:
http://code.google.com/apis/maps/documentation/javascript/examples/place-details.html