Chrome: If you've ever visited a website for an event and then forgotten to plan for it, SpotOn.It for Chrome can help you with your scheduling. The app intelligently searches sites you visit for events listed and offers to add them to your Google Calendar with one click.
I've been trying the extension, and it works for major events, concerts and community calendars. Now, if I want to remember that there's a free movie in the local park this weekend, all I have to do is visit the community calendar, click the button in the Chrome Toolbar and add the event to my Google Calendar so I'll be reminded in advance. The add-on even lets you know if the event will run up against appointments on your calendar before or afterward.
SpotOn.It is actually a service that recommends things for you to do in your area and can fill gaps in your Google Calendar, but it's currently limited to a handful of cities and events. The Chrome extension has no such limitations and works on virtually any website. Plus, you can use the extension to quickly add your own events to your Google Calendar at any time -- just click the button and choose "Add Custom Event".
You'll have to give the service limited access to your Google Account for the service to work. If you use your calendar often and want a quick way to add events and announcements you see on the web, it doesn't get easier than this.
SpotOn.It - Add to Calendar [Chrome Web Store]