Share your calendar
In Google calendar, go to Settings (link is in the far upper right of the page), Calendars, click on the calendar's name.
Note: you can only share calendars which have been made public. If it hasn't been made public, click on Share this calendar before proceeding. You will have the option to make it public (which allows anyone to see it) or you can make it available exclusively to the specific people you choose. Change your settings as you wish, then click on Calendar Details to get back where you were.
To give people a url they can visit themselves:
Where it says Calendar Address, click HTML. Copy the displayed link.
To put your calendar inside a webpage, blog, etc:
Where it says Embed This Calendar, click on Customize the color, size, and other options. Play with settings to your desire. When you're done, click Update HTML. Copy and paste that code into your own site.