MandrillForm for Craft is very similar to Pixel & Tonic's ContactForm plugin, but uses Mandrill for sending emails instead of your native mail server (if you have one).
{% macro errorList(errors) %}
{% if errors %}
<ul class="errors">
{% for error in errors %}
<li>{{ error }}</li>
{% endfor %}
</ul>
{% endif %}
{% endmacro %}
<form method="post" action="" accept-charset="UTF-8">
<input type="hidden" name="action" value="mandrillForm/sendMessage">
<input type="hidden" name="successRedirectUrl" value="success">
<h3><label for="fromEmail">From Email</label></h3>
<input id="fromEmail" type="text" name="fromEmail" value="{% if message is defined %}{{ message.fromEmail }}{% endif %}">
{% if message is defined %}
{{ _self.errorList(message.getErrors('fromEmail')) }}
{% endif %}
<h3><label for="fromName">From Name</label></h3>
<input id="fromName" type="text" name="fromName" value="{% if message is defined %}{{ message.fromName }}{% endif %}">
{% if message is defined %}
{{ _self.errorList(message.getErrors('fromName')) }}
{% endif %}
<h3><label for="subject">Subject</label></h3>
<input id="subject" type="text" name="subject" value="{% if message is defined %}{{ message.subject }}{% endif %}">
{% if message is defined %}
{{ _self.errorList(message.getErrors('subject')) }}
{% endif %}
<h3><label for="message">Message</label></h3>
<textarea rows="10" cols="40" id="message" name="message">{% if message is defined %}{{ message.message }}{% endif %}</textarea>
{% if message is defined %}
{{ _self.errorList(message.getErrors('message')) }}
{% endif %}
<input type="submit" value="Submit">
</form>
Right now I've built this plugin very quickly to meet the very specific needs of another project I'm working on. So I've done the bare minimum to get this working, but the more I interact with Mandrill, the more I like the service so I definitely plan on extending the functionality.
This plugin currently includes v1.0.55 of the Official Mandrill API Client for PHP. The latest wrapper can be found on this packagist repo.