Yay!!! Oh, I so hope all the original actresses come back--I thought The Sisterhood of the Traveling Pants was one of the better book-to-movie adaptations, and a lot of that was because of the cast. Plus, I'm excited that it's getting a sequel, and that it'll be going right to the fourth book, so that you'll have that growth in the characters.
Sam Raimi Confirms Spidey 4, 5, and 6
This is slightly less exciting, since we don't know anything about who's gonna direct, whether Tobey Maguire and Kirsten Dunst will come back, etc. Since it's frankly unlikely, IMHO, that any of those three will return, I'm waiting to see whether I should look forward to this or not.