Moved plugins to root directory. I'm ditching the idea of shipping plugins with themes until it's more obviously necessary. This way it's easier to merge and update plugins.

plugins/gist_tag.rb

@@ -0,0 +1,94 @@
+# A Liquid tag for Jekyll sites that allows embedding Gists and showing code for non-JavaScript enabled browsers and readers.
+# by: Brandon Tilly
+# Source URL: https://gist.github.com/1027674
+# Post http://brandontilley.com/2011/01/31/gist-tag-for-jekyll.html
+#
+# Example usage: {% gist 1027674 gist_tag.rb %} //embeds a gist for this plugin
+
+require 'cgi'
+require 'digest/md5'
+require 'net/https'
+require 'uri'
+
+module Jekyll
+  class GistTag < Liquid::Tag
+    def initialize(tag_name, text, token)
+      super
+      @text           = text
+      @cache_disabled = false
+      @cache_folder   = File.expand_path "../_gist_cache", File.dirname(__FILE__)
+      FileUtils.mkdir_p @cache_folder
+    end
+
+    def render(context)
+      if parts = @text.match(/([\d]*) (.*)/)
+        gist, file = parts[1].strip, parts[2].strip
+        script_url = script_url_for gist, file
+        code       = get_cached_gist(gist, file) || get_gist_from_web(gist, file)
+        html_output_for script_url, code
+      else
+        ""
+      end
+    end
+
+    def html_output_for(script_url, code)
+      code = CGI.escapeHTML code
+      <<-HTML
+<script src='#{script_url}'></script>
+<noscript><pre><code>#{code}</code></pre></noscript>
+      HTML
+    end
+
+    def script_url_for(gist_id, filename)
+      "https://gist.github.com/#{gist_id}.js?file=#{filename}"
+    end
+
+    def get_gist_url_for(gist, file)
+      "https://raw.github.com/gist/#{gist}/#{file}"
+    end
+
+    def cache(gist, file, data)
+      cache_file = get_cache_file_for gist, file
+      File.open(cache_file, "w") do |io|
+        io.write data
+      end
+    end
+
+    def get_cached_gist(gist, file)
+      return nil if @cache_disabled
+      cache_file = get_cache_file_for gist, file
+      File.read cache_file if File.exist? cache_file
+    end
+
+    def get_cache_file_for(gist, file)
+      bad_chars = /[^a-zA-Z0-9\-_.]/
+      gist      = gist.gsub bad_chars, ''
+      file      = file.gsub bad_chars, ''
+      md5       = Digest::MD5.hexdigest "#{gist}-#{file}"
+      File.join @cache_folder, "#{gist}-#{file}-#{md5}.cache"
+    end
+
+    def get_gist_from_web(gist, file)
+      gist_url          = get_gist_url_for gist, file
+      raw_uri           = URI.parse gist_url
+      https             = Net::HTTP.new raw_uri.host, raw_uri.port
+      https.use_ssl     = true
+      https.verify_mode = OpenSSL::SSL::VERIFY_NONE
+      request           = Net::HTTP::Get.new raw_uri.request_uri
+      data              = https.request request
+      data              = data.body
+      cache gist, file, data unless @cache_disabled
+      data
+    end
+  end
+
+  class GistTagNoCache < GistTag
+    def initialize(tag_name, text, token)
+      super
+      @cache_disabled = true
+    end
+  end
+end
+
+Liquid::Template.register_tag('gist', Jekyll::GistTag)
+Liquid::Template.register_tag('gistnocache', Jekyll::GistTagNoCache)