A website that constantly updates with the latest iPad app price changes and updates to apps is called Appshopper. It’s a good place to check for the latest sales or updates to apps for your iPad.
You can even download an Appshopper app for your iPad or iPhone.
You can set up an account with Appshopper and request alerts for when apps you may have are updated or an app you may be interested in goes on sale. Basically, you add apps to your own personalized list. You can modify that list from your iPad, iPhone or web.
The site also works for iPhone apps.
Be careful…its addictive and you will find yourself constantly checking.