My favorite brand is Creative Grids. They don't slide. They are the easiest to read and they aren't yellow. Yellow is very difficult for me to see so I boycott Omnigrid.
My favorite two are the 6 ½ by 24 ½ and the 2 ½ by 6 ½. I need another of the smaller one so I can keep it downstairs. It was a gift. The other was also but I think it is around $24