Shows a email contactform on your blog as a static page. It can be accessed by either the custom permalink or by index.php?serendipity[subpage]=contactform. You can customize the look of the contact form by putting the plugin_contactform.tpl file into your template directory and modify it there. Captchas from the Spamblock plugin (if enabled) will be applied.
Flattr is a social micropayment platform that lets you show love for the things you like. This plugin embedds "Flattr"-Badges in blog entries and RSS feeds. You can specify flattr-specific options per-entry, with a default global fallback.
This plugin offers special UTF-8 alphabetic sorting as an extension so specific plugins like Freetag. It allows to sort by kyrillic and other foreign characters with a custom alphabet. Alphabet contributions are welcome (on the s9y forums).