Here's some simple step by step instructions for installing a Google Calendar in your site.
First, create a google account and create a calendar, with whatever settings and entries you want. Then click on the small arrow beside the calendar you want to embed in the left column. Select calendar settings.
On that page you will see a bit of code in a text box in the Embed This Calendar section. Cut and paste it to page code.embed.calendar.
Finally, wherever you want to show the calendar, put [(embed calendar)]. Depending on the site' skin, you may need to edit some of the parameters to fit the calendar to your page. That's all there is to it!
This is how it looks: