Today I found it's nice to work with ctags, which is a source code analysis tool.
Although it doesn't have a nice front-end gui interface, ctags works nicely with vi and vi's brothers, e.g., vim, gvim.
The source navigator is also nice to try, but it looks much complicated when you just want to have a look at the classes or functions in your code. The other important thing is I am used to program in GVIM.
The way to use ctags is very simple, first go to your source directory, and type following command in your terminal:
ctags -R *
this command will generate a tags file which you can find in your source directory.
Next thing is using vi or gvim to open your source file, and move cursor to the keyword, e.g, class name, function name, etc., and use CTRL-] to get this keyword's source position. If you want to get backward, then use CTRL-T.
CTAGS is small and big enough for me.