This is from Blog Kindle:
I was recently looking around for an easy way to open FB2 eBooks on one of my Kindle. I’ve tried some FB2 to Mobipocket converter in the past and it failed miserably so I gave up on the idea for a while. Recently I gave it another try. This time around I’ve tried to convert FB2 files to PDF. I’ve stumbled upon a marvelous web-service – http://fb2pdf.com/ – it does what it’s name implies. You upload FB2 file and download PDF. The service can even save you a roundtrip and download FB2 files directly from websites like http://lib.rus.ec/. When converting you can specify target device: Kindle 2, DX, Sony, etc so the resulting PDF is optimized for a particular screen size. I couldn’t me happier!