Safari Knows About Its Open Pages
I noticed a thoughtful touch in Safari recently (it is probably new in Safari 5).
If Safari receives a request to open a web page that is already open in a window, it shows the window and reloads the page. I would improve this by just showing the window and not reloading, but nevertheless this is much better than opening another window containing a duplicate of the page.
Actually, this only works with a specific setup that happens to be what I use. That is: windows, not tabs, and not using Safari’s toolbar. I load pages using Alfred. You can see this behaviour from anywhere there are links. For example, messages in Mail or any kind of document.