What’s a good way to add a calendar inside WordPress pages or posts?
Add the calendar widget to the side bar. In WordPress, click "Appearance" followed by "Widgets." Now you need only drag the "Calendar" to the sidebar of your choice (depending on your theme.)
Justin, I think he is looking for something to embed right inside the posts. I don't widget will do here.
@ Robert, if I am not mistaken 30Boxes calendars can be embedded onto any we page.