Jetpack is a WordPress plugin for your self-hosted WordPress site that brings you all sorts of useful thing. For one thing, more security. It blocks malicious activity, scans your site for problems, and backs up everything. That backup thing is very great. I just needed it yesterday! But my favorite feature is the Site Search. It replaces the default WordPress site search (which isn’t very useful) with an entirely new search experience. Not just the UI of search, but it improves the search results dramatically. I use Jetpack on all my WordPress sites.