Scott (@scottsweb)

Add Google style instant search and search suggest to your WordPress powered site. This plugin will begin displaying search results as soon as your site visitor starts typing into the search box.
The plugin requires very little configuration and should work out of the box with most themes. The plugin has its own options page to configure the plugin to work with your theme if you require it.
<a href="http://scott.ee/" title="WordPress designer and developer" rel="nofollow ugc">a plugin by Scott Evans</a>

Instant Search & Suggest

Instant WordPress search with search suggestions for tags, categories and titles.

richardphelps

This plugin allows users to chat in real time using AJAX. Users can connect with any other users.
Use the [bp-instant-chat] shortcode to embed the front end chat on any page.

BuddyPress Instant Chat

Instant chat plugin for BuddyPress allowing user to connect and talk in real time.

Instant Search & Suggest vs BuddyPress Instant Chat