I have a dirt cheap Crucial V4 64GB SSD for my OS and my most used programs, i then i have two, 320GB Hard Drives from Hitachi that i got given from my dad, one for my Games and mass storage (or which there is very little) and the other is for my Video recordings from things like DXtory and Fraps
(My old, 5200rpm 1TB drive i got from an old computer i put in my girlfriends PC).
I basically just run this because its cheap, the Crucual V4 64GB only cost me around £35 (Thats around $55 USD) and even though its only SATA 3GB/s its still a vast improvement over a mechanical drive!