I attended FOSDEM last weekend, Europe's biggest Open Source conference. Can you imagine a largely self-organising conference that manages to somehow come up with 500(!) talks for two days? That's FOSDEM.
With so many talks to choose from, I only managed to attend a total of 10 (not counting one spontaneously organised "Birds of a Feather" session). Interestingly, I noticed one common design element on the slides of 3 of these (pretty much randomly selected) talks: A progress bar.