The 62 AAU members already mentioned are tops:
http://aau.edu/about/article.aspx?id=5474
Plus there are the 108 universities that are considered Carnegie “very high research universities” here:
http://carnegieclassifications.iu.edu/lookup_listings/srp.php?clq=%7B%22basic2005_ids%22%3A%2215%22%7D&start_page=standard.php&backurl=standard.php&limit=0,50
And 99 more universities that are Carnegie “high research universities” here:
http://carnegieclassifications.iu.edu/lookup_listings/srp.php?clq=%7B%22basic2005_ids%22%3A%2216%22%7D&start_page=standard.php&backurl=standard.php&limit=0,50
Note that pretty much all of the AAU members are also Carnegie very high research universities. As an fyi, University of Nebraska was an AAU member for about 100 years, but was removed from the list in recent years when the organization changed the way it adds up research dollars.