I was unable to get that 'AJAX Page Loader 1.5' plugin to work with the latest version of Wordpress (currently 3.1.2). So I did MUCH digging around and found this tutorial 'How To AJAXify WordPress Theme' which was super easy to follow and worked like a charm!
This plugin will extend Buddypress to have an Ajax Chat client that works with Buddypress groups, as well as all WordPress users. As of version 1.2.6 Buddypress Ajax Chat works with both WordPress MU and WordPress Single User. Ajax Private Messages WordPress Plugin. The first 100% Ajax Powered private message.
The aim of social networking sites is to connect people with the same interests and having the ability to chat with other members is one of the best ways to do that. If you want to include a chat component to your BuddyPress social networking site, the BuddyPress-Ajax-Chat plugin will do just that.

Buddypress Ajax Chat App
Buddypress Ajax Chat Bot

BuddyPress Ajax Registration plugin allows your users to register quickly on your website. User can register from any page of your website. The plugin not only registers them but also logs them to the website automatically. This plugin is responsive and works well on mobile devices.

Buddypress Ajax Chat App

If you want to provide a pleasant joining experience to your site users, this plugin will help you. It is also compatible with almost all themes and will work out of the box. If there is any issue, Our support is here to help.

The best buddypress plugin ever. Users will be able to login smoothly with no screen refreshes on errors Notification Emails. Manage and customize all the users notification emails easily from the back-end dashboard.

Features:

Easy Registration using Ajax and the modal box
Easy Login using the modalbox
Easy Forget Password feature.
You can tune each feature.
Users can login/register from any page of the site
Automatically logs the new user to website
Will increase the participation of users( As they can register and login on a specific page without any redirects )
Allows you to control which xprofile fields/groups are shown( programatically )
Developers/Designers have full control over layout( Yes, you can theme the popup as you want and also control the template if you want )
Compatible with BuddyPress on WordPress(standard) as well as WordPress Multisite(Including blog registration)
fully responsive and works on mobile devices
Live username availability checker ( with BuddyDev Username Availability Checker plugin )

You can control the layout/look and feel using the template files.

Screenshots

Let us see some screenshots first

Here is the registration screen

Modal window is responsive:-

Buddypress Ajax Chat Bot

If there is an error, the user will be notified immediately as shown below

And if the registration is successfull, user sees the welcome message and is then logged in to the current page

The message will appear for 1 second( You can control it from the javascript file ) and then the page will be refreshed to make the user login.

Admin settings:-

Please see the documentation page for all the details.