Thank you so much! I sometimes wish to download flv, but more often I am looking to extract an image from within jQuery or Flash shell, and that is what I used the "Activity window" for most often.
The solution you are showing is exactly what I wished for, and is much more efficient than the previous way!
It's still possible to download videos without any additional plugins, you just have to do it a slightly different way, explained below;
(Actually this first step is optional, as the keyboard shortcut works whether the Develop menu is enabled or not)
First, make sure the "Show Develop menu in menu bar" checkbox is ticked from Safari, Preferences -> Advanced, it's at the bottom.
Secondly, go to the page where you want to download the file from.
Thirdly, either go to the Develop menu, and choose "Show Page Resources" or press the shortcut ⌥⌘A (A with Cmd and Alt held down) which is the same shortcut as the old Activity Window;
This will open the Page Resources inspector, which if you haven't seen it before can be quite confusing, but don't worry. What you're looking out for is a little finger pointing cursor icon in the top right hand side of the middle bar, that looks like this;
Click that and then click on the video you want. When you mouse over the video, or any other element of the page, it should turn blue. Clicking this shoud take you to the link to the video in the page source code as shown in the Inspector at the bottom. Mouse over that, so it underlines in blue and right click on that link and choose "Edit Attribute" what you're after should be highlighted.
Copy that to your clipboard with ⌘C.
Click on your downloads icon in the top right hand side of Safari, and press ⌘V. There's no indication that you can do that, but you can. Your download should begin.
Viola! Job done with no plugins.
This seems to be a pretty popular gripe with Safari but all that's how to do it.
Hope that helps
I was missing Activity too but it is not completely gone although it´s a bit different.
Hitting alt-cmd-i opens the developer window.
You got to choose "Show Developer in the menu" in Safari/Preferences.
You get a window with three columns. In the left column you have some hirarchy. One of which is called Others. Here on my german system it is Anderes. This one contains movies currently played. Similar to Activity.
If you found the proper line click on it. In the right column, under Location you will find the complete Url which you can copy, similar to Activity.
i use and like many of the safari extensions for flv/youtube/html5 etc but a more general solution for the missing activity monitor list is provided by hetima with SafariStand https://discussions.apple.com/message/20651191#20651191