MHT files are IE only, but there is a Firefox plugin called UnMTH that'll open and save MHT files.
You can also save as PDF with pdfdownload http://www.pdfdownload.org/
Have you seen the Firefox addon called "Scrapbook":
# Linux kernel on:
- Desktop 3.0GHz AMD A8-3870
- ASUS Eee 1001PX
- LG-P500 Smart Phone
- Raspberry Pi