Roland Rust

Prints out your webservers php settings as well as other information about your WordPress installation. 
Important for posting at various WordPress support forums.

Phpinfo

Prints out your webservers php settings as well as other information about your WordPress installation.

ray.viljoen

Fubra

Adds custom menu under WordPress Admin to view all PHP info as produced with the standard phpinfo function, but without breaking the page strucure.
Developed by <a href="http://www.catn.com" rel="nofollow ugc">PHP Hosting Experts CatN</a>

PHP Server Info

A very simple plugin for displaying full PHP Info from within the WordPress Admin menu.

Phpinfo vs PHP Server Info