adx is a minimalistic but massively Web-enabled address book that runs completely in your Web browser. It's OS-independent and supports comprehensive details for each contact entry, including user identifiers and profiles for Skype, Twitter, Flickr, Delicious, Facebook, LinkedIn, studiVZ, instant messengers, etc. It supports the hCard and XFN microformats.
Google Calendar Chrome Extension adds a button to your browser toolbar that displays a preview of your calendar while you're navigating. (works on any page). If you're on certain sites where it detects the presence of events, the icon changes to a green "+". Clicking that icon lets you add the event to your Google Calendar, and shows you a Map (if there's a location it could detect.) Supported sites include Facebook, Evite, and any site that uses the hCalendar microformat or derivative microformats such as hResume.