Starting today Overview has two new plugins pre-installed on overviewproject.org. You can access both through the Add View menu.
WordCloud is just that. You can click on a word to select all documents containing that word.
Multisearch looks for many search terms in all documents at once.
You can add items one by one, or click Edit entire list as text to paste in lots of search terms at once. After you’ve added a search you can edit the query by clicking the Edit link to the right. In this example, the search named “environmental” actually searches for “environmental OR environment”. You can also do fuzzy searches by adding a ~ (tilde) to the end of the query, like “Obama~” which can be incredibly useful for searching through documents that have been poorly scanned and OCRd. Multisearch supports the same advanced query syntax as Overview’s regular search.
Both of these plugins were written using Overview’s new plugin development API, and you can write your own!