Lee Filters
Lee makes 4 series being, sev5n (compacts), 100mm, SW150 and bug (GoPro). View here.

Cokin
Cokin makes 4 different series being A Series, P Series, Z Pro and X Pro. View here.

Gron
Gron GR-150 a Chinese made version. Try eBay.

Kood
View here.

Formatt Hitech
Hitech make a Formatt-Hitech Holder (100mm, 85mm and 67mm) and a Locruit Holder (100mm & 165mm) system, view here.

NISI
NISI Square Filter System here and here.

Progrey G150X
Model here. Review here.

The FilterDude
Good quality filter holders and adapter plates, without the premium Lee price tag, here.

VU filters
View here.

Wine Country Camera Filter
A great piece of kit, but costs an arm and a leg. Review here.

Wonderpana
View here.

The Wonderpana FreeArc XL filter system is designed to fit the Canon 11-24mm wide angle lens.

Good overview of various filter holders here.

What should I buy?
Whatever you want or need, suggestions here. For me The FilterDude Holder gives great quality without a high price tag. It can used with many lens.

You need a specialist holder where your lens has a bulb protruding like the Canon 11-24mm or Nikon 14-24mm lens.