well you can check the following: Their Alexa ranking at www.alexa.com Their google cache at google.com - cache:sitename.com Their google index stats at google.com - site:sitename.com Their google backlinks at google.com - link:sitename.com Their yahoo backlinks at yahoo.com - link:sitename.com
When it comes to ranks - Alexa for non US, compete for US.. Those tend to be at least reasonably accurate..