quite old (1999) but still inspiring: a data visualization of users based on their past online social interactions, to inform users about each other & the overall social environment.
each user is represented as a flower, & each flower petal conveys a personal message (posted in a newsgroup or forum), ordered by time in a clockwise fashion. petal color brightness represents time, whereas pistil-like circles on top of the petals denote responses. the height of a flower represents how long a user has been in the board, as indicated by time of first posting. this uses the metaphor that a flower planted earlier is taller than one planted later.
see also flower garden. [mit.edu (pdf)]