I noticed that the Kindle fonts hacks have been, more or less, distributed all over the place. There are many hacks (for all three devices) contained within the Kindle International hack page, others in the general hack page, etc.
So, I thought it would be good to created a thread specifically dedicated to custom font hacks, that work on all three devices. Here are some, please feel free to post your own, and your feedback. As always, screenshots are appreciated.
All links below are for all three devices, running 2.3, signed so no pre-jailbreak is needed:
Droid Sans (full formatting)
Droid (only sans serif regular, but Cyrillic, Chinese, Japanese and a bunch of other languages are supported)
GNU FreeFont (All font styles are preserved, but these fonts only support Latin and Cyrillic characters)
Droid (full formatting, but only Latin characters)