ePub Bud is a free tool for creating books for the iPad. It does this in a number of ways. Either you can send a book to the company and they say they will digitize it for free, you can upload an existing digital copy and it will be converted on the site, or you can use the WYSIWYG interface to write straight into the site.
I tried uploading my Web 2.0 Tools for Teachers manual from the PDF format and this is what it came out like. You can download it from here if you are lucky enough to have an iPad Web 2.0 Tools for Teachers iPad edition
The process of uploading it was pretty simple. Once you are registered you just click on 'Upload', locate the file in the usual way and click again to upload it. Once the file is uploaded, it takes a short while to convert it to the format for iPad.
When it has been converted the status will change from 'unprocessed' to 'Converted to ePub'. You can then share the link with anyone who wants to read your materials or book on their iPad. You can set privacy status on the file and add tabs and index it. You can even edit the file once it's uploaded using the on site WYSIWYG.
This is a great way to convert content for use on the iPad. It doesn't have to be books of course, you could also use it for worksheets, or notes for your students or books or stories they have created themselves.
It's also worth checking out the books that are already there too as there is quite a collection. The focus seems to be mainly on children's books at the moment. Have a look in the 'browse' section and see if anything takes your fancy.
Now all you need is an iPad!