It is rare that I get impressed by something, but I have to admit that balsamiq has managed to really impress me.
Balsamiq mockups is a flash application that you can use to very quickly build a UI mockup. That in itself is not really new. What is new is that they have somehow managed to take this to a completely new level from the point of view of usability. It took me 7 minutes, from first use of their program, to get this thing working:
Aaron Jensen talked about it as well, which is how I heard about it, and damn am I thankful for that.
To say that I am impressed is not sufficient, I am going to buy a copy just because I didn't have to (I was able to create the above picture using the free version). If I could do it, and I am so dense in matters of UI that I cannot draw a straight line with a ruler, that is saying a lot. That I could do it so far, that is saying even more.