Jeffrey Schutzman

Memcached Object Cache provides a persistent backend for the WordPress object cache. A memcached server and either the 
the PECL Memcached or PECL Memcache extension and class are required. Detects either the PECL Memecache or PECL 
Memcached (Memcached preferred) class and uses the appropriate interface. That means you don’t need to figure out 
which PHP class is available in your installation, the plugin will detect the proper configuration.
This plugin does not require manual copying of files between directories for installation, and it doesn’t require the installer 
to differentiate between the memcache and memcached PECL extensions if they know their host makes once available.
Also, because this plugin autodetects the PECL extension available, for those that develop on Windows where the 
PECL Memcached extension is not generally available, you can maintain a common configuration with your Linux host 
where that extension is common.
Plugin creates a dashboard menu option under “Tools” where you can view your memcached statistics.
Plugin is based laregly on previous works by Matt Martz, Ryan Boren (https://wordpress.org/plugins/memcached/) and 
Scott Taylor, Ryan Boren, Matt Martz, Mike Schroder ( https://wordpress.org/plugins/memcached-redux/ )

MemcacheD Is Your Friend

Adds MemcacheD object cache support to WordPress and auto-configures your cache setup.

Automattic

Mark Jaquith

Mohammad Jangda

Andy Skelton

Yoav Farhi

vnsavage

orensol

Batcache uses Memcached to store and serve rendered pages. It can also optionally cache redirects. It’s not as fast as Donncha’s WP-Super-Cache but it can be used where file-based caching is not practical or not desired. For instance, any site that is run on more than one server should use Batcache because it allows all servers to use the same storage.
Development testing showed a 40x reduction in page generation times: pages generated in 200ms were served from the cache in 5ms. Traffic simulations with Siege demonstrate that WordPress can handle up to twenty times more traffic with Batcache installed.
Batcache is aimed at preventing a flood of traffic from breaking your site. It does this by serving old pages to new users. This reduces the demand on the web server CPU and the database. It also means some people may see a page that is a few minutes old. However this only applies to people who have not interacted with your web site before. Once they have logged in or left a comment they will always get fresh pages.
Possible future features:
<ul>
<li>Comments, edits, and new posts will trigger cache regeneration</li>
<li>Online installation assistance</li>
<li>Configuration page</li>
<li>Stats</li>
</ul>

Batcache

Batcache uses Memcached to store and serve rendered pages.

MemcacheD Is Your Friend vs Batcache