I've never seen this before and found it quite interesting -
http://www.infostradasports.com/asp/infostradasports.asp?page=federation_euroclubindexrankingThere are plenty of holes you can pick in the methodology but fundamentally it comes down to results over the past three years in the Premier League (and European equivalent), the Europa League, and the Champions League. More recent results are given more weight and home advantage is factored into the results. It's similar to the FIFA rankings for national teams by the looks of it.
I have to say I was surprised to see us as high as 30th (not as surprised as I was to see the Blues in the top 100!!!), especially given some of the teams below us in the list - Borussia Dortmund, Juve, Dyanmo Kyiv, Schalke, CSKA Moskow, etc, etc - all seasoned Champions League teams. That said, we have finished 6th in one of the toughest leagues in Europe in the past three seasons so in that respect it makes sense. Rapid Vienna are 94th - just emphasises what a monumental cock up it was to get knocked out by them again!!!
There are a few other stats around the site, and in the annual report on there. Interesting stuff.