Google added some time ago an expandable box (called PlusBox or ManyBox) next to search results connected to local businesses. Now they're experimenting with a Finance Plus Box, that shows financial information next to the homepage of a business listed on a stock exchange.
But this is only the beginning. Unlike OneBoxes that are query-dependent and are displayed at the top of the search results, a Plus Box is added next to a search result, regardless of the query. Plus Boxes show information from different Google services that are highly relevant to a site.
If you consider the case of a local business, it's clear that many people want the address of the business and how to get there. If you search for "oil company", it's nice to see additional information about companies, like the stock quote.
Google also experimented with a Plus Box that shows facts from a site and also a search box that lets you search inside the site.
In another experiment, Google showed related blog posts and important pages from the site:
Other Plus Boxes that should be available in the weeks to come:
* a Google Scholar Plus Box that shows information about scholar papers: the abstract, the number or quotes, the number of pages and links to Google Scholar.
* a Google Video / YouTube Plus Box that shows a small player where you can preview a video inside the search results.
This is a unique feature and Google will continue to add Plus Boxes for different kinds of sites. The universal search engine is closer.