As with swivel, users can upload any data set, but the tools for visualizing and graphing the data are much richer. The visualization options include US and World maps, line graphs, stack graphs, bar charts, block histograms, bubble diagrams, scatter plots, network diagrams, pie charts, and treemaps. The site isn't yet live, but should be very shortly. Meanwhile, you can get a good sense of the types of graphs available by checking out the visualization gallery.
I asked Martin and Fernanda how they compared themselves to swivel, and Fernanda replied:
You also asked if we see our site as "Swivel for visualization". That phrase isn't quite accurate (any more than Swivel is "Many Eyes for data" ;-). Both our site and Swivel are examples of a broader phenomenon, which we call "social data analysis," where playful, social exploration of data leads to serious analysis. At the same time the two sites fall on different ends of a spectrum. Swivel seems to have some neat data mining technology that finds correlations automatically. By contrast, we've placed our emphasis on the power of human visual intelligence to find patterns. My guess is that both approaches will be successful because social data analysis is a powerful idea.
In Many Eyes our goal is to "democratize" visualization by offering it as a simple service. We also think that there's something special about visualizations that gets people talking, so we placed a big emphasis in design and technology to let people have conversations around the visualizations.
Personally, I'd love to see swivel and manyeyes working together, as swivel already has some great data sets, but has only a limited number of graphing tools. But that's an exercise for the future. For now, data wonks can just rejoice that both sites exist, and should start exploring, and as Martin says, conversing about what they find. I love both of these sites.