A SATA Controller Card is an expansion card that is utilised so that your motherboard can support SATA Hard Drives (as opposed to just standard Hard Drives).
However, SATA controllers are only really required for older moterboards which don't support SATA. As it stands, most modern motherboards will support SATA-II (300Mb/s). For example, my motherboard (ASUS P5N32-SLI premium) supports 6 x SATA II devices.
The only other time you may need a controller would be if that amount of connections was not enough.
As such, if you get a motherboard that has SATA connections, you will not need a SATA Controller Card.
Hope that helps!