Shared contacts has a UI in the Premium edition of Googles Apps for domains.  And I think the API works for all domains.

It's not really clear to me how contacts are shared across users - or which ones are?

The Google Search API can be used by directly calling the URL and getting JSONP formatting data back.  They recommend this for "non-JavaScript" environments where you can use the Search API library directly.  But it's also a nice light-weight way to get search results into a web page.

Currently only 65 sample Wave Gadgets in the gallery.

The API for GitHub is all read-only now. Would be really cool to have an API to read and WRITE Gists in GitHub!

Here's the Google Sites API.

Awesome - Google is making sure that Google users *own* their own information and can migrate it in and out.

Quoted: The Data Liberation Front is an engineering team at Google whose singular goal is to make it easier for users to move their data in and out of Google products.

Quoted: The Google Sidewiki Data API allows client applications to view Google Sidewiki content in the form of Google Data API feeds. Your client application can use the Google Sidewiki Data API to request a list of Sidewiki entries and query for Sidewiki entries that match particular criteria.

Cool how-to from the Google I/O conference - how they used google maps to make a conference map.

Very cool (simple) samples of accessing your Google data from a third party site.