Among Google's websites, Gmail is now number 2, trailing only to Google search, but Gmail is still under 10% of all visits.
Gmail’s top 3 sources of traffic were Google, Facebook, and Yahoo! Mail, totaling 58% in February 2009. Google accounts for the largest share of upstream traffic at 49%, which has increased 10% from February of last year. Facebook represents just over 4% of the upstream traffic and this share has nearly doubled when compared to the previous year. The third source of traffic, Yahoo! Mail, presumably from Internet users with multiple web-based email accounts, sent fewer referrals in Feb 2009 and the share declined 18%.