Y.Kohno

This is a flexible search form widget. 
You can easily generate a multi condition search form and display anywhere as widget.
複数のカスタムフィールド、投稿タイプ、カテゴリー、タグでの検索が可能な複合検索フォームを簡単作成できるプラグイン。ウィジェットで好きな場所に設置可能。
Currently supports 
– Custom Fields 
– Taxonomies 
– Categories 
– Post tags 
– Post Type

WP Meta Search

Search form for searching through custom fields, post types, categories, tags, and free text.

Samuel Diethelm

This plugin enables the use of [if] shortcodes to work with conditional logic based on the existence of post meta or taxonomy terms on posts and pages.
Please consider taking a minute to rate the plugin or let me know any feature request. Thanks!
<h4>Taxonomy</h4>
With conditional logic for taxonomy terms, you can use names, slugs or term_ids:
<ul>
<li>[if taxonomy=”category” slug=”cars”]Content to show[/if]</li>
<li>[if taxonomy=”category” name=”Cars”]Content to show[/if]</li>
<li>[if taxonomy=”category” id=”123″]Content to show[/if]</li>
</ul>
<h4>Post Meta</h4>
Post meta (or custom field) logic can be used to check if a certain meta_key AND meta_value combination are present or just a meta_key:
<ul>
<li>[if postmeta=”car_model”]Content to show if car model info is present[/if]</li>
<li>[if postmeta=”car_model” value=”Tesla Model S”]Content to show if car model is Tesla Model S[/if]</li>
</ul>

Logic Shortcodes

Use shortcodes for conditional logic based on post meta or taxonomy terms.

WP Meta Search vs Logic Shortcodes