You should find XCode on the install CDs which came with your iBook. I'd be very surprised if that didn't do it.

If you prefer, head over to versiontracker.com or macupdate.com and search for "C++ Compiler". You should find something. If not try sourceforge.net or macforge.net. You may have to work a little harde to find what you want, but it will be there somewhere.

Like I say, Xcode is free, and nicely polished and you already have it. If you install all the developer tools from your discs, you should be able to just compile your existing programs and run them from the Terminal if you prefer.