I don't have a Kindle but I have learned the following:
- Kindle can read Mobipocket books as long as they don't have DRM (Digital Rights Management)
- BookDesigner can make Mobipocket format books from text, DOC, RTF, and HTML files
- Better quality Mobipocket books can be made from Mobi Creator (HarryT has a tutorial around someplace on this site about how to do it)
- You can download free Mobipocket books from MobileRead and load them to your Kindle through your PC
I hope this helps and welcome to MobileRead.