Oh no.
Well, this is one I can definitely give advice on. At least in terms of having experience with it -- you know that sozlet went through the same thing last year, moving away from her best friend, Jack. (Although in a rather complicated twist, he moved away from her first, a week before us; but they were close enough that we went out to see them one last time before we moved for good.)
It absolutely sucked. Pretty much the suckiest part of the whole sucky moving episode.
One thing that seemed to help is that we took lots of pictures of everyone -- Jack, sozlet, Jack's little brother, Jack's dog, Jack's iguana -- and made a little photo album out of it. She looked at that thing over and over again for a long time after we moved. She STILL likes to get it out and talk about it now and then. It is a cheap one from Walgreen's that has a little cut-out in front, first picture is one of Jack smiling a really sweet smile, and she just -sigh-s whenever she sees it.
We also had a few phone calls -- not sure why we haven't done more, the first was a big hit. And some cards, parental emails, etc.
Do you know anything about who will be moving in? As callous as it may seem, the biggest cure for Jack angst was meeting new kids -- once she started preschool and met her current best friend, Jack was still there in the background as someone very special to her, but not an ongoing source of angst. (As he was, or his absence was, from moving day 'til the first day of preschool.) She'll still talk about him apropos of nothing in particular.
Trying to think of what else we did to prepare. We read "Little Bear's Friend", which ends with Emily going away and Little Bear being sad about that, but staying in touch via letters. We had a specific timeline and talked about it a lot. Jack's moving in 10 days -- 8 days -- 6 days -- this is the last time we will play at Jack's house, but we will go visit his new house. Our last visit with Jack will be in 3 days. Our last visit with Jack will be tomorrow. This is it, our last visit with Jack. (Ugh, it was awful -- description here):
http://www.able2know.com/forums/viewtopic.php?p=779893#779893
Then after that we wrote some letters, and the phone calls. And we just waited it out.
Of course, there was all the extra stuff about US moving -- I'm sure that makes everything a little different.
Will think more.
I think the anger stuff is really normal. Defense mechanism. Jack and sozlet had some awful fights the last week or so. The end of the day that I took all kinds of photos for the album, they got in some hysterical screaming fight, us leaving early with sozlet sobbing, etc. I forget the cause, he wouldn't let her play with a toy or something.
They had a great time that last day, though.