Mobi2mobi can handle Kindle AZW files and can change some of the metadata in DRMed Kindle books. You can obtain mobi2mobi in the Mobiperl package available from https://github.com/szarroug3/X-Ray-Creator/tree/master/MobiPerl
Use the following mobi2mobi command to change the Kindle display title for your DRMed Kindle books:

mobi2mobi --output [output filename] --exthtype updatedtitle --exthdata "[Corrected Title]" [original AZW filename]

A great source of e-book conversion utilities can be found at http://wiki.mobileread.com/wiki/E-book_conversion. There you will find various commercial, opensource and freeware programs that can handle file formats like LRF, CHM, LIT, HTML, PDF, RTF, PDB and DOC and convert them to formats that the Kindle can handle.

I’ve used the opensource Calibre EBook Management Software and can recommend it without hesitation. It’s available for Windows, Linux & the Apple  OS X platforms.

Amazon Kindle File Formats

• AZW
• TXT
• MOBI
• PRC

Note that Amazon offers its conversion via email service for the following file formats;

• Word DOC
• HTML
• JPEG
• TXT
• GIF
• PNG
• BMP
• PDF (experimental, results vary)

Software like earlier mentioned Calibre can handle additional formats, such as;

• CBZ
• CBR
• CBC
• CHM
• EPUB
• FB2
• LIT
• LRF
• ODT
• PDB
• PML
• RB
• RTF
• SNB
• TCR

Ran across a neat hack to download free e-books from feedbooks.com using Kindle’s Whispernet. It’s documented at http://www.feedbooks.com/help/kindle and works by downloading a book that contains embedded links to downloadable e-books that can be downloaded via Whispernet for free.