Where is the "about" (like in facebook) or similar on Twitter for email address?

Click on the name or organization; it will bring up their “page”. Over on the left side, there is a column of information about the person or entity that will have either an email address or the URL to their website.

However, not many people display their email address on twitter. You can direct message them through twitter, just click on the little envelope under their tweet.

Thanks @zenvelo