Here are some useful mod_rewrite rewrite examples that you can use in your .htaccess file. Some of my favorites.
RewriteEngine On RewriteBase /
Sometimes your rewrites cause infinite loops, stop it with one of these rewrite code snippets.
RewriteCond %{REQUEST_URI} ^/(stats/|missing.html|failed_auth.html|error/).* [NC]
RewriteRule .* - [L]
RewriteCond %{ENV:REDIRECT_STATUS} 200
RewriteRule .* - [L]
This is probably my favorite, and I use it on every site I work on. It allows me to update my javascript and css files in my visitors cache's simply by naming them differently in the html, on the server they stay the same name. This rewrites all files for /zap/j/anything-anynumber.js to /zap/j/anything.js and /zap/c/anything-anynumber.css to /zap/c/anything.css
RewriteRule ^zap/(j|c)/([a-z]+)-([0-9]+).(js|css)$ /zap/$1/$2.$4 [L]
When you use flash on your site and you properly supply a link to download flash that shows up for non-flash aware browsers, it is nice to use a shortcut to keep your code clean and your external links to a minimum. This code allows me to link to site.com/getflash/ for non-flash aware browsers.
RewriteRule ^getflash/?$ http://www.adobe.com/shockwave/download/download.cgi?P1_Prod_Version=ShockwaveFlash [NC,L,R=307]
On many sites, the page will be displayed for both page.html and page.html?anything=anything, which hurts your SEO with duplicate content. An easy way to fix this issue is to redirect external requests containing a query string to the same uri without the query_string.
RewriteCond %{THE_REQUEST} ^[A-Z]+ /.*\ HTTP/
RewriteCond %{QUERY_STRING} !^$
RewriteRule .* https://www.askapache.com%{REQUEST_URI}? [R=301,L]
This mod_rewrite code for your .htaccess will 301 redirect and request for askapache.com/anything to www.askapache.com/anything
RewriteCond %{HTTP_HOST} !^www.askapache.com$ [NC]
RewriteRule ^(.*)$ https://www.askapache.com/$1 [R=301,L]
This .htaccess rewrite example invisibly rewrites requests for all Adobe pdf files to be handled by /cgi-bin/pdf-viewer.php
RewriteRule ^(.+).pdf$ /cgi-bin/pdf-viewer.php?file=$1.pdf [L,NC,QSA]
For sites using multiviews or with multiple language capabilities, it is nice to be able to send the correct language automatically based on the clients preferred language.
RewriteCond %{HTTP:Accept-Language} ^.*(de|es|fr|it|ja|ru|en).*$ [NC]
RewriteRule ^(.*)$ - [env=prefer-language:%1]
This rewrite example denies any request with a request_method other than the specified request_methods with a 403 Forbidden HTTP status code.
RewriteCond %{REQUEST_METHOD} !^(POST|GET|OPTIONS|PUT)$
RewriteRule .* - [F,L]