This video offered some insights into ECW's time at the Hammerstein Ballroom (part of the Manhattan Center) in New York City. It covers the ECW shows in 2000 and early 2001 as well as the One Night Stand shows and the one show when ECW was running under the WWE company.
There is some solid history and research in this video, including pro wrestling newsletter snippets from the latter months of 2000 and early 2001 - discussing the business side of the company at the time. Despite happening during the company's last few months, it appears that the company's first two shows at the venue (August 25 and 26, 2000) were two of the most successful nights in ECW's history. Both nights had sellout crowds of 2500+ in attendance.