Consider installing Memcached
Memcached is an open-source high-performance distributed memory object caching system intended for use in speeding up dynamic web applications by alleviating database load.
Consult with your system admin first about your particular setup, but in most cases, Memcached will be a great help.
Unlike PageSpeed, this doesn’t do anything upon installing, so you need to configure your sites to use it. If you use WordPress, it plays nicely with W3 Total Cache plugin and you can set Memcached to do the caching.