I believe I've seen it done real time on a Microsoft IIS server back when I was an intern (many years ago), but that's not a transparent proxy. I am willing to bet a transparent proxy could do this, as has been stated already.
Other than that, I did a quick google search. Maybe with a span session with output to a server running this?
http://www.httpdebugger.com/http/http_packet_sniffer.html
I haven't tried it myself, just a suggestion.