Caching php scripts (intermediate opcode) in memory can make your dynamic pages load really fast and exert less load on the CPU of your VPS.
Typical php caching engines and accelerators are eAccelerator, xCache and APC (a PECL extension). APC is considered the best.
In this do-it-yourself tutorial, I've written about APC and easy step by step procedure to get it installed on your VPS.
Here's the complete tutorial : Cache PHP Scripts With APC PECL Module
So, try it out today; lessen system load and watch your dynamic pages fly!
Feel free to submit comments and social bookmark the blog post...many people may be helped with this.