Projectbook is an interesting take on a notebook/diary/todo/task manager for the iPad. It is project oriented, so it's useful for something like building a toolshed, setting up a company meeting or lots of daily tasks. It allows you to have all your notes, photos, audio and documents in one place. New entries are indexed and tagged. Web pages, documents and other items that are external can be 'emailed' to Projectbook. More about that later.
The app accepts files from Dropbox and Instapaper, and lets you set up reminders or repeating events. You can write in formatted text, with styles like underlining supported. There are extensive sorting options, and the ability to share files as PDF, HTML or plain text.
The workflow needs a little getting accustomed to, but help is extensive, both online and built in. The built-in help could be improved, however. It is several pages long and you can't exit until you reach the end, which is a bit of a pain. Searches are quick, and unless you are exporting or importing, you need not be online to use the app. It's perfect for an airplane trip or places where network connectivity is not available.