How to make ubuntu use more RAM to cache a specific set of binaries?

There is a rather lengthy tutorial on the forums you might like:

http://ubuntuforums.org/showthread.php?t=1594694

The guide basically explains how to create a squashfs image out of your existing Ubuntu installation and copy the entire image to RAM upon boot to speed up your OS. I will also go into some detail of how to make your /home mount from a regular hard drive thereby making sure the important information one would wish to save on their machine would remain untouched between boots.

See the guide for details.

Three keywords to google and some helpful links:

Change swappiness: How do I configure swappiness?

/tmp to RAM (): How can I use RAM storage for the /tmp directory and how to set a maximum amount of RAM usage for it?

Disable access time: http://intensecogitation.info/2010/06/15/optimizing-ubuntu-debians-file-system-by-disabling-access-time/

These there were also lately covered in Hak5 for laptop battery optimization but these tricks should be also useful for your as the way to save power is to use less of that good old hard disk: https://www.youtube.com/watch?v=XloTXFgNL7s