Network/HTTP debugging tools

Since I'm working on CalDAV/CardDAV, Exchange Web Services and Zimbra SOAP APIs, I often need to see what's happening on the wire. To achieve this, I use a couple of tools:

• tcpflow (installed with MacPorts). tcpflow allows use to see TCP trafic, on a specific network interface. You can use rules to specific which host(s) or port(s) that you want to sniff, which is quite useful. But since it log the packets, if the data is encrypted, you can't see unencrypted.
• Charles Proxy. Since I really need to see the unencrypted data (my Exchange hosting provider only allow HTTPS), I'm using Charles to act as a HTTP/HTTPS proxy. Charles is really great, it will show SOAP or REST request/response in a nice layout, and the greatest thing: it can act as a HTTPS proxy, so you can see the unencrypted data! The only downside is that I wasn't able to get it to work with Outlook 2011 and a HTTPS Exchange server (it will always return a 401 Not Authorized response).
• Debug window in Zimbra. You can use some query arguments when logging into Zimbra Web Client, arguments that will allow use to see the SOAP requests that the client is sending to the back-end. Very useful when looking for values that Zimbra is sending.
• Debug mode in iCal. If you don't want to use a proxy, you can see what's iCal (or Calendar on 10.8) by enabling the log for HTTP activity made by iCal. To do so, just run:
  
  defaults write com.apple.iCal LogHTTPActivity -boolean TRUE

Update: a friend on Google+ sent me a link to a Wireshark tutorial. I must admit that I prefer tcpflow for low level debugging, but Wireshark and tcpdump are indeed other kind of tools who can use (lsof is also a tool that I used to find what applications and services are using for networking and file handles).