I love the Virtual Manipulatives web site out of Las Vegas, NV. Unfortunately, their website is Java based which means I cannot use it on the ipads in my classroom. Since I lasted visited the website, the Virtual Manipulative folks have gotten together with a company to produce an app for computers so students can still use the manipulatives while off line.
The app is made by Matti Math and is designed to be installed on a computer so students can work either on a Windows or Mac off line. It means there is no need for an internet connection, no need for Java, but it is only designed for the computer, not for tablets yet.
Unfortunately, I do not have easy access to computers because there are like 3 carts of computers for the middle school/high school and that means you have to sign up in advance. You could use the computer room but that is often in use by the elementary school students.
I know that I can get certain individual apps through the itunes store but there are times I do not want to download a bunch of single apps that do the same thing, the one web site does. It takes less memory that way. On the other hand, this is a nice website if your students are using computers with a decent internet connection.
The National Library of Virtual manipulatives cover grades preK to 12 in Numbers and Operations, Algebra, Geometry, Measurement and Data Analysis. Many of the apps within the library cover several grades and can be used for different classes. I know that using the apps on my Mac, I get the message that I need to activate the Java and then I'm told its out of date, do I want to update it.
I'll be checking a couple other websites to see if they can be used on the ipads. Its a wish of mine but who knows if it will actually happen.