The native format for Stanza is ePub, which is the Open eBook standard from the International Digital Publishing Forum (http://www.idpf.org/). ePub is supported in Stanza Desktop, iPhone, and iPod Touch, as well as in Adobe Digital Editions and the next generation of e-ink readers like the Sony Reader (PRS-505).

There are a number of ways to create ePub content:

1. Calibre (http://calibre-ebook.com): a free tool for Windows, Mac OSX, and Linux that allows you to convert to ePub from a wide variety of formats. Calibre currently does a better job than Stanza Desktop at preserving styles and formatting of source documents.
2. Adobe InDesign (http://www.adobe.com/products/indesign/): InDesign is a high-end publishing tool for authors and publishers, and supports the creation of ePub files.
3. Feedbooks (http://feedbooks.com/share/): You can log into Feedbooks and create your own content, which will be made available in ePub, as well as other formats like PDF and Kindle. In addition, any books you create and share will automatically be included in the "Free Books by Feedbooks" section of Stanza's Online Catalog under the "User Created Books" area, so you don't need to download and transfer the book separately.
4. BookGlutton API (http://www.bookglutton.com/api): If you have your book in HTML format, you can convert it into ePub using their online conversion API
5. ePub Tools (http://code.google.com/p/epub-tools): Command-line tools suitable for batch processing and integration into toolchains. Includes tools for conversion from Word, RTF, DocBook, TEI, and FictionBook.
6. Adobe PDFXML (http://labs.adobe.com/technologies/mars) - Per Adobe's blog, this is useful for making small changes to existing EPUBs.
7. eScape - ePub Creator (http://www.infogridpacific.com/igp/AZARDI/eScape%20-ODT2ePub) - "It lets you instantly and effortlessly turn Open Office Writer documents (ODT) into perfect ePubs..."
8. eCub (http://www.juliansmart.com/ecub) - "a simple to use EPUB and MobiPocket ebook creator"
9. Sigil (http://code.google.com/p/sigil/) - "Sigil is a multi-platform WYSIWYG ebook editor. It is designed to edit books in ePub format."
10. Easy EPUB (http://www.easypress.com/products/aqpep/) - By simply uploading your InDesign or Quark book files, EasyEPUB will quickly produce a fully compliant EPUB version of your book within 5 minutes.
11. DNAML's PDF2EPUB (http://www.pdftoepub.com/) - Convert PDFs to EPUBs in 6 easy steps. The nice thing about this software is that it can handle headers and footers which are often challenging when converting PDFs.
12. Stanza Desktop (http://stanza.lexcycle.com): Stanza allows you to convert from a large variety of formats like MS LIT, Mobipocket, Kindle, RTF, PDF, MS Word, and many more into ePub

Ultimately, an ePub file is merely a zip file consisting of XHTML and XML metadata, so it is possible to create one "by hand" yourself. A good tutorial for this can be found at http://www.jedisaber.com/eBooks/tutorial.asp.