a DRY and unobtrusive way to use will_paginate with ajax via jQuery

_items.html.erb

<!-- app/views/items/_items.html.erb -->

<ul>
  <% items.each do |item| %>
    <li><%= item.name %></li>
  <% end %>
</ul>

<%= ajax_will_paginate items, :update => 'my_items_list' %>

application.js

// public/javascripts/application.js

function rebind_pagination_listener() {
  $('.pagination.ajax a').click(function(e) {
    $('#'+e.target.parentNode.getAttribute('update')).load(e.target.href);
    // anything else you want to happen when the pagination links are clicked goes here
    e.preventDefault();
  })
}

application_helper.rb

# app/helpers/application_helper.rb

def ajax_will_paginate(collection, options={})
  options.merge!({:class => 'pagination ajax'})
  output = will_paginate(collection, options)
  output += "<script lang='javascript'>rebind_pagination_listener()</script>".html_safe if output
  output
end

index.html.erb

<!-- app/views/items/index.html.erb -->

<div id="my_items_list">
  <%= render :partial => 'items', :object => @items %>
</div>

items_controller.rb

# app/controllers/items_controller.rb

def index
  @items = Item.all
  respond_to do |format|
    format.html
    format.js do
      render :partial => 'items', :object => @items.paginate(:page => params[:page], :per_page => 5)
    end
  end
end

Posted about this here.