Email from Night Shade informs me that The Cloud Roads by Martha Wells is free in the US Kindle store today. You have to be logged in from a US-based IP address to see it, but this link should work if you are.

This is, of course, a cunning plan to encourage you to buy the soon-to-be-released sequel, The Serpent Sea, as well, but The Cloud Roads is a good book and it is free today, so if you have a Kindle why not give it a try? My review here.