Here is the htaccess file that I use for my codeigniter projects. It is very similar to the one used by wordpress. I like it better than the one that is mentioned in the codeigniter user guide.
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?$1 [L]
enjoy!
