Rappongi is pretty much where all the foreigners go to party. There are bars and clubs and of course adult entertainment (this is Japan after all) everywhere.
I realize most people are really excited to see what Rappongi is all about, but you'll be disappointed from my review. I walked through the area quickly past all the bars and restaurants catering to westerns (TGIF, Hard Rock, etc) but drinking and partying was never my thing so I left the area quickly. I was bored. Sorry, no report.