This program switches the font in the Mobipocket viewer to Sans-Serif or Serif (the software default) depending on your choice. It's simple enough to use, you'll need shell access. Unzip, copy, and run.
Let me know if you have any problems or questions.
Note: This has only been tested on an English Language iLiad. I'm not sure what effect (if any) it will have on other languages. Install on others at your own risk.
Edit2: Another Attachment Update. 100% working version as posted by Wallcraft.