Here is a panorama I took from the Park Hyatt Tokyo (Shinjuku Park Tower), looking out towards the Tokyo Tower and Roppongi (in the corner). Click the link for a MUCH bigger HD version... 56k run away in fear as it's over 3MB
And to Babo, it is called the NTT DoCoMo Yoyogi Building (NTTドコモ代々木ビル). Interesting fact, it's not actually their headquarters, and only has 25 "floors" despite being 787 feet.
The top half of the building is actually empty and acts like a giant antenna.