Update the readme with details on user interfaces

README.markdown

@@ -17,9 +17,19 @@ resource health.
 * [Mailing list](http://oss.clusterlabs.org/mailman/listinfo/pacemaker).
 * [Documentation](http://www.clusterlabs.org/doc)
 
-## Important information about the _crm shell_
-Since late-April, the _crm shell_ is no longer included in the Pacemaker source tree.
-This change was made at the author's request as it is now maintained as a separate project at https://savannah.nongnu.org/projects/crmsh/
+## User interfaces / shells
+
+There are multiple user interfaces for Pacemaker, both command line
+tools, graphical user interfaces and web frontends. The _crm shell_
+used to be included in the Pacemaker source tree, but is now
+maintained as a separate project.
+
+This is not meant to be an exhaustive list:
+
+* _crmsh_: https://crmsh.github.io/
+* _pcs_: https://github.com/feist/pcs/
+* _LCMC_: http://lcmc.sourceforge.net/
+* _hawk_: https://github.com/ClusterLabs/hawk
 
 ## Build Dependencies
 * automake