Do you want to know about Load Balancing server? You can ask your DC if they have load balancing option for you to go for. Load balancing require an additional hardware to be setup for your server. Some example of good load balancer which I use is Barracuda Load Balancer. Your DC might have their own load balancer hardware. Not all DC offer load balancing server but you can request for it.
Unless you have several sites on one server now and want to split them up you will need a load balancer which is an option on most hosting sites.
What is eating up your server resources? IO or CPU? If it's the former, you may want to move your content to another server and make it a dedicated file server while keeping your existing server for dynamic page requests. If you are CPU bound, then what's eating up your CPU? Is it your database? If so then a load balancer isn't going to exactly solve your problem, there's a lot more factors to consider in this situation. If you can let us know what's the bottle neck is then we can give you recommendations on how one might move forward.