use usb drive as disc cache?

I see Windows suggests using a USB 2.0 drive as a faster Hard Drive Cache. Does Apple OS support this?

And besides letting the OS defrag and do other "cleanup" functions, are there other things, besides just more memory, to speed the laptop? Even when I have nothing open but Activity Monitor, and 1GB free memory, things are taking 'forever' [a min or more to open Safari while the system seems to be doing other things]. CPU is showing under 10% busy, over 50GB free hard drive, but even "Finder" locks up. Original 2GB RAM still in the system.