[copied to foundation-l and wikipedia-l; please note this when replying]
I was sure I'd seen this on the mailing lists before, but I couldn't find it on a quick search (which is odd - I'm sure I heard a week ago)
It appears the Esperanto Wikipedia is on a stamp. Well, Esperanto is on the stamp; a chunk of the text from [[eo:L. L. Zamenhof]] is used as a sort of background illustration.
Colour image: http://www.jr.co.il/pictures/stamps/jrst0399.jpg Detailed description: http://www.jr.co.il/pictures/stamps/jrst0399e.jpg Brief discussion: http://en.wikipedia.org/wiki/Wikipedia:Village_pump_%28news%29
This is quite a delightful discovery; it isn't clear why our text is used, but it must be a good motive, and it's certainly a somewhat unusual bit of recognition :-)
Congratulations to the eo.wp community - from a glance at their discussion forums last night I didn't see any obvious keywords to suggest they've noticed yet, so someone more competent than I may like to make sure they know...