I think that people are missing the point. He's asking the question, "How best to use my 2nd drive, which is a 16GB SSD."
While its true that you don't need ReadyBoost if your OS/Applications drive is an SSD, ReadyBoost CAN be useful to speed up your slow OS/Applications HDD (spinning drive).
In fact, I just started a job, where my work PC has fast CPU, 8GB memory, but a fairly slow HD. Upgrading the HD is not really an option at this point.
To speed it up, I bought a 120GB Samsung 830 SSD, and hooked it up using eSATA to my work PC. When I plugged it in, it prompted me if I wanted to use ReadyBoost on my external eSATA SSD. I said yes, and allocated 32GB initially, which I've dropped to 20GB.
ReadyBoost on the eSATA SSD has helped the slow main HDD a lot. Visual Studio 2010 now launches in 1 second, versus 4 or 5 seconds before.
I'm exploring whether I should move my pagefile.sys to the SSD also. Haven't done it yet. But, bottom line, don't be afraid to hook up an extra SSD to your system as a 2nd drive, and enable ReadyBoost.