notorioushttp

Allows developers to log variables, see the call stack, benchmark code; all to a logfile, so your page doesn’t get polluted with log messages. Each log message records the date and time, IP address, requested page, and file and line the log message came from, as well as the information to be logged.
The plugin has an options page which allows you to randomize the cookie and logfile, for security purposes; as well as turning logging on and off for a given user. (Via cookie.)
Documentation for the aaLog class can be found at the <a href="http://www.notoriouswebmaster.com/2013/07/01/aalog-a-logging-class-for-php/" rel="nofollow ugc">NotoriousWebmaster blog</a>.
Documentation for the aaLogWP plugin, which includes the aaLog class, can also be found at <a href="http://www.notoriouswebmaster.com/aalogwp-documentation/" rel="nofollow ugc">NotoriousWebmaster blog</a>, though on a different page.

aaLogWP

Allows developers to log variables, see the call stack, and benchmark code; all to a logfile, so your page won't get polluted with log messages.

Budiony Damyanov

Easy cache takes a real-time snapshot of every Page, Post, Category, Link, etc. These snapshots are then stored (cached) into folder of your choice, so they can be referenced and served to the visitor later, in order to save database processing time that has been slowing your website down.
The Easy cache plugin uses configuration options that you select from the Administration panel. Search for <code>Easy cache</code> in your <code>Settings</code> page. 
Easy cache excludes administrative or WP system login pages from caching (i.e. it works only on public part of your blog). Only NOT logged-in users (which are the most) can benefit from caching mechanism when they visit the public part of your website. Password-protected pages or posts are excluded from caching too.
There is an automatic cache expiration system, which runs through WordPress® behind-the-scene, according to your <code>Cached file expires after</code> setting, also various cache and server load statistics are available for precise tracking of what is going on.
The Easy cache plugin has been tested with various permalink settings, various pagination plugins like <code>WP Pagenavi</code> and <code>WPML WordPress Multilingual Plugin</code>, also with <code>WordPress® Jetpack</code> mobile theme, with variuos custom post types, custom queries, custom pages outside WordPress® installation directory and a number of widely used plugins, however if you experience troubles, post your issue on the plugin’s forum.
Supported languages
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English
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Spanish
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French
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Bulgarian
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bodi0`s Easy cache

Speed up your blog with Easy Cache, bullet-proof and easy-to-use website caching mechanism for WordPress that just works.

aaLogWP vs bodi0`s Easy cache