Although these two words are most times confused by most people, however, their respective meanings can never be the same. Agenda means an organized plan about what to be attended to. It is a list, usually in written form, that contains different programs that have been designed for a particular meeting. So, you can simply say that "there are different kinds of programs that have been designed as part of our agendas for today."
In other words, it also means a list of matters to be addressed at a meeting. On the other hand, itinerary means a written list of activities that have been outlined for a road trip or vacation. This usually contains all the information about where you are traveling to, your mission, and what you are expected to be doing when you get there. For instance, "I know where she could be now because I saw her itinerary before she left."