URL Rewriting for Apache (requires mod_rewrite) and IIS (requires IIS url rewrite module)

.htaccess

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . index.php [L]

web.config

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.webServer>
        <rewrite>
            <rules>
                <rule name="Main Rule" stopProcessing="true">
                    <match url=".*" />
                    <conditions logicalGrouping="MatchAll">
                        <add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" />
                        <add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true" />
                    </conditions>
                    <action type="Rewrite" url="index.php" />
                </rule>
            </rules>
        </rewrite>
    </system.webServer>
</configuration>

NGINX

location / {
        try_files $uri /index.php;
    }

nginx.conf

location / {
	if (!-e $request_filename) {
		rewrite ^/(.*)$ /index.php?$1 last;
	}
}

For some reason the .htaccess sample doesn't work if you put it in a vhost configuration.

Update: see http://tltech.com/info/rewriterule-in-htaccess-vs-httpd-conf/

location / {
	try_files $uri $uri/ /index.php?$args;
}

To follow up on @RedShift1's answer from above, if you'd like to make this work in a virtual host configuration in apache you don't need to put the .htaccess file in the project's root folder.
This is my sites-available/<my-domain>.conf:

<VirtualHost *:80>
  ServerName <my-domain>
  # You don't have to put an alias in, but it's useful
  ServerAlias www.<my-domain>
  DocumentRoot /var/www/<my-domain>/public_html/
  ErrorLog ${APACHE_LOG_DIR}/error.log
  CustomLog ${APACHE_LOG_DIR}/access.log combined
  # Note that this is in a different context now - not in the virtual host, but in the actual root directory.
  <Directory /var/www/<my-domain>/public_html/>
    RewriteEngine On
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule . index.php [L]
  </Directory>
</VirtualHost>

try_files $uri $uri/ /index.php?$args;

Works man.

NGINX

location / {
        try_files $uri /index.php;
    }

That will lost $_GET contents.