I was in Philadelphia today on a journalism assignment, and it was a typical digital moment: I was simultaneously talking to my girlfriend Emily, who was in New York, on the phone, and instant-messaging with a few friends on my Danger Hiptop. In the middle of a sentence, her phone went dead. Then, a minute later, all the New-York-based people on my instant-messaging buddy list went offline.

The moment was a creepy echo of 9/11 — everyone in New York suddenly vanishing. Thankfully, my non-New-York friends were still online, so I quickly IMed with them and found out what was happening; they were getting the news off CNN.com. I began to realize I was probably stranded in Philly, because Amtrak was also shut down. But I wanted to know more, and surfing via the Hiptop isn’t great when you’re in a big rush. So I got my IM friend to do a quick hunt for hotels with wifi, figuring I’d check into one.

As it turns out, I walked by Rittenhouse Square — a downtown Philly park — and figured it might have some free wifi nearby. Bingo: No sooner than I turned my laptop on than I had about four different strong signals. None had WEP turned on, but all had customized access-point names, which suggests they were left open intentionally for others to share. Once online, I got filled in on all my travel options (bleak, of course) and booked a nearby hotel. When I got to the hotel, I found it had ethernet, but the drivers for my ethernet card were busted. No problem: I wandered down to the park and quickly downloaded the 2.5-meg driver database, thanks to the fine philanthropic wifi sharers of Philadelphia. Then I headed back to my hotel room, where I am right now.

A nice day to illustrate a few of my favorite memes-du-jour: The wonderful crisis-value of portable Hiptop-style phones, and of open community wifi.