AFAIK there is no such poster.
Qt is more than 800 classes, there was some poster showing the class hierarchy (without the methods), but including all methods? That would be a complete wall ;-)

I think I have seen or heard about something like it, but indeed: it is too big to be useful. Qt has broken the 1000 public class mark already, I think.

I don’t see the point in having such a huge poster….cheat sheets are good if they are compact and to the point, having a wall deco doesn’t help in finding the right class….

I fully agree: I don’t think it is useful, but it might be nice decoration :-)

If you use google, you could find the class chart of Qt 4.3 [doc.qt.nokia.com]

There were even other discussions about this on dev net [developer.qt.nokia.com]