Seems like a good format to follow, though I have to expand a bit...
Where: GTA (West Mississauga/Milton/Oakville area)
What: Three N800s (see notes below)
When: Got my first one in Nov. 2007 from DirectCanada out in BC.
How/Explanation: My brother bought a 770 directly from Nokia USA when they first came out a few years ago and I'd sort of inherited it/started using it with the initial goal of running a web-based front end for a home automation system on it. That then digressed into an EBook reader (thanks FB Reader you rule!), which then started fitting in with my project of a wifi device/mp3 player/crazy thing for my Jeep. So the 770 became my web front-end for controlling MPD in the Jeep. Once prices dropped on the N800 I picked one up, figured out what an awesome VOIP device it is, and with OS2008 just being released times were golden! My Dad, who travels a lot, saw it and thought it was one of the most awesome things on the planet because it meant he could make phone calls, do video chats while on vacation, look up airline websites/etc without having to drag his laptop with him (which he'd been doing for just the airline websites thing...). He bought an N800 from tigerDirect in January once they received new stock and the reduced price. He then asked me if he could hook up one of those rubber roll-up keyboards (he'd found one in tiger direct while he was there) so he could use it On the Road... which lead me to ITT, which lead me to building those USB OTG adapters!

Of course that lead to me kind of messing up my own tablet with the first few USB adapters I built that were terrible things, but since I was selling them through work here my boss said "hey if we're gonna sell this stuff, let's buy you another tablet to make up for things", which then left us with an extra N800 around the office... that we then started using for doing wireless testing and installations (we're a network cabling company). Best Wifi tool out there hands down for testing, web interfaces, ssh'ing, etc.

For me biggest uses personally are now IM (my friends still can't get over the fact that I can chat on MSN while walking around and just get messages all the time by noticing the blinking LED...), VOIP calls (ahhh SIP how I love thee... esp. since my brother runs his own VOIP service ;o) ), emailing, web browsing, and most recently it makes a damn good alarm clock in the mornings! Also managing my linux boxes with ssh, controlling the playlists/music in the Jeep, etc. Oh, and of course, remote control for Mythbox and Home automation ;o)

As for others... Haven't seen any "in the wild", but then how often do you notice what kind of phone random other people are using?... but personally I know of : My bro's old 770, which he recently upgraded to an N810; my dad's N800, the N800 here at the office, my own N800, my buddy who works at Cogeco in Burlington's got an N800, two of his co-workers also have 'em, my boss' wife has a 770 for ebook reading, oh, and the other N800 I've got for a special project ;o)

(and if you ever notice a wifi AP pop up on your available connections that's labelled "Jeep" that counts as an "in the wild" spotting ;o) )