For one, it's releasing an experimental user interface for Gmail based on the HTML5 mobile web app developed for the iPhone and Android. It features a two-pane view with a conversation thread listing on the left and message pane on the right (screenshot below).
Several Google services will also ship pre-installed on the iPad as apps: The YouTube app supports HD viewing and commenting, and the Maps app utilizes high-resolution imagery from satellite and Street View, and includes a new terrain view.
Google is the default search engine in the Safari browser, and the Google Mobile App with voice search has been adapted for the iPad as well -- this one's not installed by default, but you can pick it up at the App Store.
Notably, Google also chooses its words carefully in order to leave room for "other tablet computers" coming along soon after the iPad itself -- many of which will run Android, as we wrote about back in January.
It will be interesting to watch whether or not Google will start to play favorites with its apps for iPad versus the coming onslaught of Android (and most likely eventually Chrome OS) tablets.