At IBM’s developerWorks (cool! a site with javaCasing ;)) I found a couple of nice and interesting articles about Eclipse. Both about using it and extending it. Because Eclipse is not just a Java IDE, in fact it’s a general IDE which contains a Java plugin (the JDT). Here’s an article about what is Eclipse and why it was developed. Another article entitled “C/C++ development with the Eclipse platform” shows that you can also use Eclipse for C/C++ development (there’s also a PHP plugin). If you already read my Eclipse tour, you might also want to read this getting started guide (not as in depth as mine of course ;)).
And last but not least, if you feel like developing your own Eclipse plugins, those articles may be interesting: