I went though a 6 week plateau from March to April. Then in one week I finally went down 1 pound, and I was happy for the new low. The next week I went down another pound during the week, then 6 pounds during that weekend (3 on Saturday, 3 on Sunday).
I've done similar (6 pounds over 2 days) once since then, and just this week went down 3 pounds in 2 days.
Before the plateau I had been a very steady 2 - 3 pound per week loser spread throughout the week. Now my weight seems to hold steady and then make weird quick drops. I haven't really made huge changes in my plan, except that as I've gotten lighter (and my knees can take it) I've been walking a lot more than I used to.
My average loss per week before the plateau was 2.7 lbs, after was 2.3 pounds, and now is 2.6 pounds, so I'm now at almost exactly where I would have been with a steady loss and no plateau. Bodies are kwaaazy!