Cisco has made available a lot of data about the most popular sites on the 'net via one of their open source projects:
Cisco Umbrella 1 Million - OpenDNS Umbrella Blog
The blog post explains the methodology
It sounds like it could be more reliable in some respects than most of the other data sources out there at present
Cisco Umbrella 1 Million - OpenDNS Umbrella Blog
The blog post explains the methodology
It sounds like it could be more reliable in some respects than most of the other data sources out there at present