class ActionController::Request # ActionController::AbstractRequest in Rails < 2.3
  # Returns true if the request seems to come from a bot
  def bot?
    user_agent =~ /\b(Baidu|Gigabot|Googlebot|libwww-perl|lwp-trivial|msnbot|SiteUptime|Slurp|WordPress|ZIBB|ZyBorg)\b/i
  end
end

#
# Then in your controllers you can do :
#
# unless request.bot?
#   ... Log, stat ... 
# end