I just started experimenting with Protovis yesterday but could not find even a simple example showing how to put together a line chart. Although the Protovis website lists a large number of beautiful visualization examples, most of them were over my head as a beginner (when first looking at the code, it reminded me of The International Obfuscated C Code Contest--you can do a lot in a small amount of code, but that doesn't mean it's gonna be understandable).
The problem was one of documentation--although Protovis has a fairly fleshed out set of docs including a multi-page "quick start" tutorial, I was still searching for some simple examples to work through on my own. The problem was, I didn't realize that the icons on the left side of the docs page were clickable--I thought they were just there for aesthetics!
Now I'm good. Although I'd still love to see some very simple time series visualizations.