Ruby Pagination Logic with DataMapper and Sinatra: http://jocap.github.com/Ruby-Pagination-Logic/

app.rb

# @app.rb
[...]
require "ruby_pagination_logic"
get '/page/:page' do |page|
  @page = page.to_i
  limit = 5
  offset = RPL::paginate @page, limit

  @post = Post.all :limit => limit, :offset => offset, :order => 'date'

  haml :posts
end

posts.haml

-# @views/posts.haml
%section{:class => "articles"}
  - @post.reverse.each do |post|
    %article
      %h2
        =post.title
      = post.date
      %div
        = post.text
%a{:href => "/page/#{RPL::next @page}"}
  Next