I think there is a big Google update coming ahead - anyone else notice this on any of their websites?
Nope, not much for the few I just checked though a few page 1 gains on some terms I checked where I have gained an extra link or two so have more of the first page blanketed but this is not unusal in any way
Moz has an excellent index of changes here: http://mozcast.com/. They have a rolling real-time update daily and their expert Dr. Pete usually gives some insight to big changes when they forecast them
Isn't this just called Google Dance? It's normal to see a change in your SERP! Just be sure to continue following your SEO strategy!