I like the gmail related links concept, but it can use some improvements.

I got a confirmation e-mail for a flight I'm making. First, the link to Google Map in Gmail was to the address of the Airline's company's location(useless). What would have been useful is a map view to the city of my destination or the city I'm departing from.

The link to calendar was good. It recognized the date of my departure, and the date of return. Nice. I just had to click the link, and add a little more detail in the description field.

In the case of the flight confirmation e-mail there was more than one locations in the email, but the link to the airline was the one I did not need(in contrast, there were more than one "add to calendar" link, one for the departure date, and the other for return date).

A good feature would be to allow the user to highlight the address or event in the e-mail, click a button and go to a map or create a calendar event.

Your last suggestion might be done as a Firefox extension, or maybe Google will do it via the Google Toolbar for Firefox. Hmm, the last time they had this auto-highlighting for locations in the toolbar, it caused some controversy...