www.zdic.net has a huge amount of information on each word and character, with lots of historical citations to show how the meanings have changed over time: it's like a Chinese OED. It's almost entirely in Chinese, but there are often short English glosses of definitions.

我一般用這個网站查一查汉字的来源。有一個汉字查不着，就是"做"字。 http://www.fantizi5.com/ziyuan/

You're looking for zhongwen.com. I'm not an expert, but my understanding is that Chinese etymology is more controversial than English etymology, because a lot depends on how much you trust conclusions reached by early authors versus what actually appears on early inscriptions.