Probably the best way to learn wxWidgets is by reading the source of some 50+ samples provided with it. Many aspects of wxWidgets programming can be learnt from them, but sometimes it is not simple to just choose the right sample to look at. This overview aims at describing what each sample does/demonstrates to make it easier to find the relevant one if a simple grep through all sources didn't help. They also provide some notes about using the samples and what features of wxWidgets are they supposed to test.
There are currently more than 50 different samples as part of wxWidgets and this list is not complete. You should start your tour of wxWidgets with the minimal sample which is the wxWidgets version of "Hello, world!". It shows the basic structure of wxWidgets program and is the most commented sample of all - looking at its source code is recommended.
The next most useful sample is probably the controls one which shows many of wxWidgets standard controls, such as buttons, listboxes, checkboxes, comboboxes etc.
Other, more complicated controls, have their own samples. In this category you may find the following samples showing the corresponding controls:
|wxCalendarCtrl||Calendar a.k.a. date picker control|
|wxListCtrl||List view control|
|wxTreeCtrl||Tree view control|
Finally, it might be helpful to do a search in the entire sample directory if you can't find the sample showing the control you are interested in by name. Most classes contained in wxWidgets occur in at least one of the samples.