Amazon's Kindle runs GNU/Linux, which is no surprise given its suitability for these kind of consumer systems. The Kindle is fast establishing itself as the leading ebook platform, so, at first blush, that might seem unalloyed good news for free software.
Sadly, though, Amazon has also proved that it is no great friend of freedom - first, by embracing DRM for its books, and secondly, by cravenly disabling the text-to-speech capability because The Authors' Guild has eighteenth-century ideas of what copyright is about.
Against that background, new entrants to the e-reader market that run GNU/Linux are particularly welcome, since they offer hope that not all ebooks will be viewed on locked-down devices.
Here's one, with the rather hubristic name of Cool-er, which has the bonus of being British (although it doesn't seem available here yet). It's too early to say how hackable it will be, and whether it will be able offer features like text-to-voice, but it's likely to be the first of many such alternatives to the Kindle, and that's got to be cool.
Update: @codepope has reminded me that the FAQ seems to suggest that the Cool-er reader isn't compatible with GNU/Linux. In fact, I checked, and this only refers to anyone benighted enough to want to use Adobe's DRM; for texts that don't have manacles, GNU/Linux works fine, I am assured.