The last few days I've seen some buzz about Plotly. The best write up I've seen of it was on the Make blog, authored by Jack Palmer - CEO of Plotly. Clearly he'd know the product fairly well, but may not be the most impartial judge. Still his guide through the features of Plotly is well written and has some good examples showing data from Arduino and Raspberry Pi.
It appears to be a simple method of displaying your data in a number of useful and aesthetically pleasing ways. Think we'll give plotly a whirl!