Emma Watson wrote an entry in her Emma Messaging System (EMS) wishing everyone a Merry Christmas. She also mentioned that she is back on set and filming again for the next Harry Potter movie.

From Emma Watson:
Hey everyone!
I have just finished my first week back on set at Warner Brothers, and I was so excited to be in the studios again! I have started filming the sixth Harry Potter film and it's going really well.
There are a few new faces around set, such as Jesse, who plays the character Lavender, who is really cool, although our characters really don't get on in the film! We have actually just finished filming a scene with Lavender and Ron kissing, where Hermione gets really jealous which was quite fun!
Only a few days to go now until Christmas, I'm so looking forward to seeing all the family and having some quiet time! I hope you all have a wonderful Christmas and I will update you with all the news in the New Year!
Lots of love Emma x