Splitting the workload evenly between the two would be extremely difficult unless you have multiple static IPs and either a DNS server or DNS on one of your two web servers. However, if you have session data, I'm assuming you're using php/mysql. What you can do fairly easily, is to make one machine a web server and the other a mysql server. Then simply change your db-connect or mysql-connect or whatever your include is, from
mysql_connect(localhost, root, password)
mysql_connect('local ip of sql server', root, password
You'll need to make a few changes in your firewall and security settings, but this way one machine will handle the site and web requests, while the other handles queries. The effectiveness of this depends on your site to a point. It'll come down to overall traffic vs. queries/db traffic. But it will help to split up the workload with minimal difficulty.