What are the best tools for producing infographics - attractive displays that combine graphs, diagrams and text to convey a lot of information succinctly. I'm interested in both web-viewable content and posters for printing.

Specifically, I'm asking:

• What combinations of tools are used (eg, one tool for making graphs, another for assembling graphs and text into the final infographic)?
• Are any vector graphic tools (eg, Illustrator) particularly more or less suited to the task than others?
• Are there any online tools which are useful in the assembly process?

(As an example of the kind of thing I'm interested in making [but on much more modest scale], http://xkcd.com/980/)