Hacker News Reader

This looks nice but until Kindle supports EPUB it's a no-go for me.

i haven't seen an EPUB that calibre couldn't convert into a MOBI with less than good results.

I find that some more advanced things get messed up pretty badly and need manual tweaking (ie table of contents).

I've been using Liberator, a much better reader which supports epub, djvu and other formats (sorry, couldn't find a download link).