If this has been answered already, I haven't found it...
By default, all of my blog categories display on the main page, which is fine. Alternatively, readers can choose a specific category to read. However, I would like to give them the option of selecting - or filtering - multiple categories. For instance, if I have categories named "travel", "sailing", "cycling", "africa" and "south america", I would like my readers to be able to select to view all posts posts that have both the "cycling" and "south america" categories, and exclude all other that have neither. Is there a plugin for this? Or is it a matter of creating my own custom search page? If the latter, is there a source of advice in creating this somewhere?