- Precision of translation (the more the better)
- Copyability (no tables, strange HTML formatting, etc.)
- Freedom (as in beer)
- Anybody can ask a question
- Anybody can answer
- The best answers are voted up and rise to the top
Chabad.org has great translation with Rashi commentaries. It's the best you can find online.
Unfortunately, the two best websites for getting english translations are not Jewish in origin.
But it is hard to deny that they fit all of your criteria.
Biblegateway might win because of its search features and multple layouts which you can get results, and you can see large sections of text at a time if you wish such as this: http://www.biblegateway.com/passage/?search=Genesis+1&version=YLT
In general, in biblegatway, "Young's Literal translation" will most likely match the Jewish translation better than the others.
Breslov.com also has the JPS translation, which is supposed to be fairly accurate. But it's navigation is a bit lacking. http://www.breslov.com/bible/