pycdep is a tool for analyzing and visualizing C/C++ header file dependencies. A script extracts information about your code and dumps it in a Prolog database, which is used to query the dependency graph. It comes with a large number of predefined queries for finding out which files include or depend on which other files, how files depend on another file, circular dependencies, transitively implied dependencies, and design rule checks (limitations on which project can include from which other project). Visualization is supported by dumping graphs to .dot files. It also has the beginnings of a natural language interface.
CodeQuery is a tool for indexing and then querying or searching C, C++, Java, and Python source code. It builds upon the databases of cscope and ctags, which are processed by the cqmakedb tool to generate a CodeQuery database file. This can be viewed and queried with a GUI tool. The features include auto-completion of search terms and visualization of function call graphs and class inheritance. The following queries can be made: Symbol, Function or macro, Class or struct, Functions calling this function, Functions called by this function, Class which owns this member or method, Members and methods of this class, Parent of this class (inheritance), Children of this class (inheritance), Files including this file, and Full path for file.