Here is how to easily rename the “category” slug that is in every WordPress install by default.The easiest way is the best way here you go >
Here is a simple plugin that works 100% for the current wordpress version 3.5+
The plugin name is WP Remove Category Base it will remove the category word from the permalinks of your blog. It is easy to implement and works for any non-technical or technical user. Though there were some decent plugin in past that used to do the same work but now they are all uncomptaible with the latest 4.2.2 version.So this one worked for me and so i am sharing. You can still access your old url and it won’t show any 404 error if you want to go a step ahead you can try 301 redirect to that old structure in case you have done link building for that previous structure.
Download link http://bit.ly/1O4BfOo