MarcusPope

A WordPress plugin that converts all URL formats to root-relative URLs to enable seamless transitioning between staging/production host environments and debugging/testing from mobile devices, without the use of hackish tactics like textual find-replace strategies or risky hosts/NAT spoofing strategies.
With Root Relative URLs you can browse your development site from http://localhost/ or http://127.0.0.1/ or from a named network resource like http://mycomputername/ without worrying about links redirecting you back to your site’s URL.
This plugin also modifies the tinyMCE hooks so links and media embedded with built-in tools will only insert URLs from the first forward slash after the domain (i.e. the root of your site.) This means when you push content changes to a staging or production environment they are guaranteed to reference the correct target instead of accidentally referencing a production resource in development or, worse-yet, a development-exclusive resource in production.
It supports path-based MU Installations, but does not support domain-based MU sites due to architectural deficiencies in the WordPress core.
Version 1.5 fixes an infinite redirect problem that is a result of a core bug in WordPress. If you have problems with the <!–more–> tag or permalinks for custom post types, please read the FAQ or new Install Steps for support.
Version 2.2 allows for adding certain URL’s or partial URL’s to a blacklist, meaning I won’t use root relative urls, but dynamic absolute URLs instead for displaying content. This will fix problems with 3rd party plugins, and can be configured on the General Settings page.
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Root Relative URLs

Converts all URLs to root-relative URLs for hosting the same site on multiple IPs, easier production migration and better mobile device testing.

joshbuchea

Perform a 301 redirect from an uppercase URL to the lowercase version for all non-admin URLs (that do not include a filename).
Please help by reporting any bugs or feature requests at the link below.
Bugs:
<ul>
<li>Report at: <a href="https://github.com/joshbuchea/wp-force-lowercase-urls/issues" rel="nofollow ugc">Github Issue Tracker</a></li>
</ul>
Questions/Comments:
<ul>
<li>http://joshbuchea.com/</li>
</ul>

WP Force Lowercase URLs

Perform a 301 redirect from an uppercase URL to the lowercase version for all non-admin URLs

Root Relative URLs vs WP Force Lowercase URLs