In 2001, LiveJournal was only a couple of years old ... Brad Fitzpatrick, brad, had started the service in 1999 to help keep up with his high school friends while at college, and folks were just finding their way over here from IRC and AOL (I joined in May 2000, as user #2663, having followed Ana Voog, ana, over with most of her AnaCam fans from the various IRC channels related to that). By September 2001, there were tens of thousands of users here, many very active through the day. When the attacks started happening, there was massive confusion out there, and the phone systems in and around New York and Washington started to bog down.
LiveJournal users began to set up communications links through their journals, reaching out to who they could, as they could. Several were even directly affected by the attacks, banshee had not headed into her job in lower Manhattan yet that morning, and was watching it from Brooklyn ... and posting about it in real time. She had an eerie follow-up to this many years later ... her transit stop for getting to work in the subway directly beneath the World Trade Center, and she had dropped off some film for development at a store in the lower levels there some days before the attack. She was surprised, at some point after they'd dug down that far in the rubble, to get her pictures sent to her ... what a shock.
Anyway, for those of us on LJ back then, it's hard to disassociate the 9/11 stuff from our experience of it in this context.