Google Top 1000 sites
Some time ago Google Ad Planner service create a list of 100 biggest sites in the world. This list is updated monthly as new Ad Planner datasets are released. The list defines sites as top-level domains.
For each site on the list, you'll be able to see:
The site category
Unique Visitors (users)
Wikimpia.org is entered in this list and it's ranked #341. We hope that we will rise in this rankings for one of the first places in the future. Stay tuned!