To compile rtmpdump v 1.9 on Mac OSX 10.6 Snow Leopard you will need to do the following:

1) Install Xcode 3.2 from the Snow Leopard Installation DVD

2) Edit the "streams.cpp" file in the "rtmpdump-1.9" folder by replacing all (two) occurrences of "MSG_NOSIGNAL" with "SO_NOSIGPIPE".