My last two jobs:

First one: One Friday afternoon, everyone in the building was told to pack up their desks and go home, and was told we'd be called if we should come in Monday. Of course, nobody was called. No two-week notice there, of course.

Second one: I gave my two-week notice, worked both weeks, turned over the job, and am still on good terms with the company. Went over there the other day (my wife still works there) to visit with some folks, and everyone was glad to see me, and I to see them. (The owner walked right past me in the hall, nodded hello, did a double-take and got all excited about seeing me. He was so used to seeing me every day that, when he saw me again, he momentarily forgot that he hadn't seen me in two months! Was pretty funny, even to him.)

Prior to collapsing under bad management and worse marketing, the first company didn't really have a consistent policy. Some people were asked to do a full two weeks, some were escorted to their desk to collect up their stuff under supervision, at least one was met at the door by police (that's a different situation), one was asked to stay until they actually started their next job. And then, of course, there were the people who should have been asked to resign but weren't, but that's also another story.