Just in case you haven't read my new thread explaining the new website I created, it's called
www.pejome.com. What it does is give you an easy way to access the 28,000+ free books from the Project Gutenberg website directly from your Kindle.
If you typically download from Project Gutenberg, the file will be in an HTML format. From that point you will have to convert the HTML to a MOBI file. After that, you will need to plug your Kindle into the computer and put the converted book on the Kindle. If you were to use my website, you can just navigate to the URL above on your Kindle's web browser, find the book you want, and the site will convert the book for you and will let you save the book on your Kindle directly. In my opinion, this is the easiest way to get a book on the Kindle from TXT or HTML.
If you decide to try PeJoMe, you can E-mail the link on the web site with your feedback if you like. Thanks!!