The routes for my site have been growing since adding pagination (/articles/older/) and tag filtering. As well as the small amount of logic for each route was getting duplicated.

I have been experimenting with real regex routes, so far some thing like this looks like it could be a good solution:

$items_per_page = 10
get /^\/article(\/older(\/\d+)?)?(\/tag\/\w*)?\/?$/ do |pagination, page, tag|

if pagination.nil?
   @offset = 0
  else
    if page.nil?
      @offset = $items_per_page
    else
      @offset = page.gsub(/^\//, "").to_i
  end

  if not tag.nil?
   tag.gsub!(/\/tag\//, "")
  end

  result = "Pagination #{@offset} <br  />"
  result << "Tag #{tag} <br  />"
  result << "captures #{ params[:captures] }"
  return result 
end

This means the following routes will be handled:
/article
/article/
/article/older/
/article/older/10
/article/tag/Ruby
/article/older/10/tag/Ruby
/article/older/tag/Ruby