Mary Doria Russell's The Sparrow has aliens who are roughly humanoid (two arms and two legs, etc.) but who inhabit a very different moral landscape. (In this sense it has something in common with Three Worlds Collide.)
Ooh, I've had that recommended to me once already this summer, and your more specific recommendation has pushed it onto my requested library holds list.
Today's post, Points of Departure was originally published on 09 September 2008. A summary (taken from the LW wiki):
Discuss the post here (rather than in the comments to the original post).
This post is part of the Rerunning the Sequences series, where we'll be going through Eliezer Yudkowsky's old posts in order so that people who are interested can (re-)read and discuss them. The previous post was The Truly Iterated Prisoner's Dilemma, and you can use the sequence_reruns tag or rss feed to follow the rest of the series.
Sequence reruns are a community-driven effort. You can participate by re-reading the sequence post, discussing it here, posting the next day's sequence reruns post, or summarizing forthcoming articles on the wiki. Go here for more details, or to have meta discussions about the Rerunning the Sequences series.