After offering it on the App Store for $5.99, Adobe sets Adobe Ideas free again. It is a universal app which you can use in your iPhone, iPod Touch or iPad.
Its current version provides a pretty good variety of functionality for drawing on-the-go in your iOS device. Draw with different brush types, sketch over existing images of your library, export your drawings to PDF and send them through email.
Go get it here before the Adobe guys change their mind.
Available on the App Store