RAM Caching - Exploiting RAM to the fullest extent possible This may seem weird, but I'm actually looking for ways to increase my memory usage. 

I have a Macbook Pro (8,1) with 4 GB that I updated to 16GB.

I really feel like I'm losing a lot for those 10 unused GB, aren't there any caching techniques that would help me put 'more useful stuff in my RAM' (assuming, of course, that I don't overflow this amount and start swapping on the HD, which would be counter-productive) ?

For instance, while looking for SSD's, I had a look at Samsung's RAPID technology that seem to do what I had in mind (although it does not seem to be compatible with Macs, and the amount of cache is not tunable ) ...

I have to add that I am perfectly *nix capable, work in a proper brewed environment and I am not afraid of the command line.

EDIT 1

I've found some links where people (manually) simlinks cache directories (for instance, Safari's) to RAM disks, any experience with that and/or soft handling that ?

EDIT 2

I am using Mavericks, OS X 10.9.2 (13C1021)
Manually tuning RAM usage is not always as smart as it seems.

Apple have spent quite a lot of time making OS X use memory as efficiently as possible, and so even when you are not using it directly, the OS will be using it as a file cache or for keeping data ready in anticipation of future use.

If you artificially limit the amount of RAM that is available to the OS by fixing some of the RAM as a RAMdisk, then you are not allowing the OS to work as efficiently as it can - and in fact could be constraining the memory available when it needs it, for a RAMdisk that might not be necessary at that time.

The OS tunes RAM usage constantly, and will ensure that it is being used to its maximum potential. Generally, this is the best use of your RAM, even if it doesn't 'look' like it's being used for anything.