Flare.
(As far as "technical stuff" goes, there's also some of that, though not much. I still think Eliezer's most brilliant work was CFAI; not because it was correct, but because the intuitions that produced it are beautiful intuitions. For some reason Eliezer has changed his perspective since then, though, and no one knows why.)
Looking at Flare made me lower my estimation of Eliezer's technical skill, not raise it. I'm sure he's leveled up quite a bit since, but the basic premise of the Flare project (an XML-based language) is a bad technical decision made due to a fad. Also, it never went anywhere.
Basically this: "Eliezer Yudkowsky writes and pretends he's an AI researcher but probably hasn't written so much as an Eliza bot."
While the Eliezer S. Yudkowsky site has lots of divulgation articles and his work on rationality is of indisputable value, I find myself at a loss when I want to respond to this. Which frustrates me very much.
So, to avoid this sort of situation in the future, I have to ask: What did the man, Eliezer S. Yudkowsky, actually accomplish in his own field?
Please don't downvote the hell out of me, I'm just trying to create a future reference for this sort of annoyance.