Erick Schonfeld of Tech Crunch wrote an awesome article about top used Google Products.
Top Used 10 Google Products in 2008;
According to Quantcast
1. Google Search
2. Google Maps
3. Google Image Search
4. Gmail
5. Google Book Search
6. Google News
7. Google Video Search
8. Picasa
9. Google Earth
10. Google Groups
According to ComScore
1. Google Search
2. Google Image Search
3. Google Maps
4. Gmail
5. Google News Search
6. Google Video Search
7. Google Product Search
8. Google Book Search
9. Picasa
10. Google Earth
Google maps is being used more than Gmail. It’s surprising i think. Quantacast’s list doesn’t seem to be true i think.