Bill Tancer of HitWise has created a category of the top 20 Google domains on the basis of the popularity of the varied Google services. Google.com holds almost 80% of the share, followed by Google Image Search with almost 10%, then Gmail with about 5.5%, followed by Google News with 1.5% and the others are all under 1%.
The surprise is that Google Image has such a dominating share of the overall Google pie. However, if you move beyond the Google sub-domains, then the collection of Google properties account for 4.3% of all Internet visits for the week ending 5/13/2006. For more of these stats visit Bill Tancer's post.