Pottermore has updated their Insider blog to let users know that Slytherin House won the House Cup and will be able to access Chamber of Secrets 24 hours before the rest of the houses.

Their Site Updates section has also been updated with more news on Chamber of Secrets:

Monday 09 July
Chamber of Secrets update:
This week, we are recording sounds for Chapter Sixteen, The Chamber of Secrets.

Tuesday 03 July
Chamber of Secrets update:
This week, we’re finalising artwork for Chapter Eight, The Deathday Party.

Monday 25 June
Chamber of Secrets update:
This week, we’re finalising artwork for Chapter Seven, Mudbloods and Murmurs, and Chapter Fifteen, Aragog.

Monday 18 June
Chamber of Secrets update:
This week, we’re finalising artwork for Chapter Fourteen, Cornelius Fudge.

Monday 11 June
Chamber of Secrets update:
Last week, we were editing sounds in the studio for the Chamber of Secrets and we’re now working on finishing artwork for Chapter Eleven, The Duelling Club.