The communication module is divided into multiple layers that 
are replacable or usable on their own.
First let's start with a list of files and a short description:

+----------------+---+-------------------------------------------------------+
| Module         | T | Description                                           |
+----------------+---+-------------------------------------------------------+
| fifo.c         | M | A simple fifo (First In, First Out) buffer            |
| memlist.c      | M | A simple memory list module                           |
| io_layer.c     | M | Communication layer for HTTP requests                 |
| io_layer_win32.| M | Communication layer WIN32                             |
| imo_request.c  | M | Posts XMLHHTP-Requests to imo.im server               |
| cJSON.c        | M | JSON parser in C (by Dave Gamble, slightly modified   |
| imo_skype.c    | M | Communication layer for imo.im Skype                  |
| skypetst.c     | X | Testing application for Skype imo.im service          |
| queue.c        | M | General Queue functions                               |
| msgqueue.c     | M | Message queue for incoming messages                   |
| callqueue.c    | M | Queue of incoming calls                               |
| buddylist.c    | M | Manages your list of buddies in memory                |
| imo2skypeapi.c | M | Wrapper for imo.im Webservice to SKYPE API            |
| imo2stest.c    | X | Simple test application for imo2skypeapi              |
| imo2sproxy.c   | M | Skypeproxy implementation to wrap imo2skypeapi        |
| w32browser.c   | M | C COM Interface to Internet Explorer for call supp.   |
| main.c         | X | Commandline interface for imo2sproxy module           |
| imoproxy.c     | X | Miranda plugin implementation for imo2sproxy          |
| skypepluginlink| M | Communication layer with Miranda Skype Plugin 0.0.0.46|
| socksproxy.c   | M | Communication layer with socket protocol.             |
| w32skypeemu.c  | M | Communication layer via Win32 Skype API emulation     |
+----------------+---+-------------------------------------------------------+
                  [T]ype is: M...Module, X...Executable (Application)


Now here is the module list with their dependencies divided into layers:

====================================================================
                      IMO.IM Communication layer
====================================================================

+------------------------------------------------------------------+
|                            io_layer.c                            |
+------------------------------------------------------------------+
| Communication layer for HTTP requests                            |
| Depends on: fifo.c, Win32:WinInet, linux:libCURL                 |
+------------------------------------------------------------------+
                                     ||
                                     ||
                                     \/
+------------------------------------------------------------------+
|                          imo_request.c                           |
+------------------------------------------------------------------+
| Communication module with imo.im                                 |
| Depends on: fifo.c, cJSON.c, io_layer.c                          |
+------------------------------------------------------------------+
                                     ||
                                     ||
                                     \/
+------------------------------------------------------------------+
|                           imo_skype.c                            |
+------------------------------------------------------------------+
| Description:      Skype protocol layer for imo.im                |
| Depends on:       imo_request.c, cJSON.c                         |
| Test application: skypetst.c                                     |
+------------------------------------------------------------------+
                                     ||
====================================================================
                        imo.im <--> SkypeAPI wrapper
====================================================================
                                     ||
                                     \/
+------------------------------------------------------------------+
|                          imo2skypeapi.c                          |
+------------------------------------------------------------------+
| Description:      Mapper for imo.im to simple implementation of  |
|                   SkypeAPI                                       |
| Depends on:       fifo.c, memlist.c, buddylist.c, msgqueue.c,    |
|                   imo_skype.c, (w32browser.c),(libpthread)       |
| Test application: imo2stest.c                                    |
+------------------------------------------------------------------+
                                     ||
                                     ||
                                     \/
+------------------------------------------------------------------+
|                           imo2sproxy.c                           |
+------------------------------------------------------------------+
| Description:       Skypeproxy implementation to wrap imo2skypeapi|
|                    for Miranda Plugin and potentially others     |
| Depends on:        memlist.c, imo2skypeapi.c, (libpthread)       |
+------------------------------------------------------------------+
                      ||                                      ||
                      ||                                      ||
                      \/                                      \/
+-----------------------------------------++-----------------------------------------+
|                   main.c                ||                imoproxy.c               |
+-----------------------------------------++-----------------------------------------+
| Description: Commandline dispatcher     || Description: Miranda IM Plugin          |
| Depends on:  memlist.c, imo2skypeapi.c, || Depends on:  memlist.c, imo2skypeapi.c, |
|              imo2sproxy.c, (libpthread) ||              imo2sproxy.c, (libpthread) |
+-----------------------------------------++-----------------------------------------+
                         |                   |                |
                         +-------------------+                |
                         |                   |                |
Communication layer:  socksproxy.c      w32skypeemu.c     skypepluginlink.c