The "My Favorites" option
 

I forget to use this option, but it really is a great tool for finding shots that have inspired us. I've been using when I see a cool shot in the "Random Images" margin. Does anyone else use this option a lot?

I wish there was a "least favorites" options. :p

Yep, I use it frequently! It's great for stealing ideas :)

I have used it on photos with things I'd like to see when I'm in the need of ideas, but... I don't know where are they stored/saved
how do I find my favorites?

Ah. I didn't even know that existed. It's quite well hidden too, I had to look around a bit to find it (under "Image Tools", to add a photo to your favourites, for those others like me).

To view them, look under the "My Stuff" link at the top of the photo pages.