Jim has used compete.com to compare the top bank sites.  Their estimate of unique users is based on their online panel in the US.

Using Snapshot, we found 31 financial institution sites with one million or more unique users in September:

Rank/Unique Visitors (millions)

1.    17.1            Bank of America

2.    16.7            PayPal

3.    11.9            Chase

4.    11.4            CapitalOne

5.    11.3            Citibank

6.    10.0            Wells Fargo

7.      6.2            Discover Card

8.      5.6            American Express

9.      5.3            WAMU

10.    5.0            Wachovia

Source: NetBanker 2.0: The one-million club: 31 U.S. financial institutions with seven-figure site traffic

Right away, I was struck with Paypal. Only Bank of America is larger in user base.  They are 60% larger than Wells.

Second, credit card sites are huge at 4, 7, and 8.

Check out NetBanker for all the analysis.