preload is a free Linux. It runs in background and records statistics about usage of more frequently-used programs. These programs are loaded into a Linux memory. Thus results is faster application startup times. From the project home page:
preload is an adaptive readahead daemon. It monitors applications that users run, and by analyzing this data, predicts what applications users might run, and fetches those binaries and their dependencies into memory for faster startup times.
There is a nice tutorial published by Techthrob about installing and configuring Techthrob under Debian / Ubuntu Linux systems.