A WebmasterWorld thread has some early reports that Google has done yet another Panda update.

Google Panda 2.4 would be the next update. We already had a 2.3 update just about July 22nd.

Some are suspecting this is a rolling update.

A senior member said:

Another person also noticed changes, but did you?

Is Google now rolling the Panda update? I am not sure, but I will try to find out if (1) there was a true update and (2) if it is rolling now.

Past Google Panda Updates:

Panda 2.3 on around July 22nd.
Panda 2.2 on June 18th or so.
Panda 2.1 on May 9th or so.
Panda 2.0 on April 11th or so.
Panda 1.0 on February 24th

Forum discussion at WebmasterWorld.

Update: Google has told me there is no update taking place for the Panda algorithm currently.