A quick beginning note: My friend d0c_s4vage has created a technical blog and posted his first text just a few days ago. The post entry covers a recent, critical libpng vulnerability discovered by this guy; the interesting thing is that, among others, the latest Firefox and Chrome versions were vulnerable. Feel free to take a minute and read the article here.
Additionally, the video and mp3 recordings from the presentation performed by me and Gynvael on the CONFidence 2010 conference, are now publicly available on the official website: link (Case study of recent Windows vulnerabilities).
A majority of the LPC /supposedly an acronym for Local Inter-Process Communication rather than Local Procedure Calls, as stated in WRK/ basics have been described in the first post of Inter-process Communication chapter, together with the corresponding, undocumented native functions related to LPC Ports. As you already have the knowledge required to understand higher abstraction levels, today I would like to shed some light on the internal Csr~ interface provided by NTDLL and extensively utilized by the Win32 API DLLs (kernel32 and user32).