If you're bothered by rivers and lack of hyphenation, check out a project I worked on a while ago, which implements the Knuth and Plass line breaking algorithm in JavaScript. Combined with Hyphenator.js, the results are nearly indistinguishable from TeX output.

http://www.bramstein.com/projects/typeset/flatland/

Earlier incarnations made it to HN before, but unlike the old version this renders in plain HTML instead of Canvas, so text can be selected, copied, etc.