Recently I found interesting search engine dedicated for searching over source code of open source projects: www.koders.com.
Firebird source base is indexed too, so you can look for something in Firebird internals very quickly. Moreover, this engine has useful plugins for Visual Studio and Eclipse IDE.
The second issue of “The InterBase and Firebird Developer Magazine” is available on the web now: http://ibdeveloper.com/issues/issue-2-oct-17-2005/.
It is available to read, discuss and provide links to your favorite articles. Don’t hesitate to comment articles and ask questions to magazine authors and editors.