Whitelines Why has it taken so long for someone to realize that the dark lines which dissect our notebook's pages only serve to distract from the content written on the page? Whitelines takes an innovative approach and replaces all those black lines with white lines. The effect is a much "lighter" looking page which doesn't detract from the words or images placed on the page yet you still have the gridded structure provided by the lines themselves.
Moleskine These are really the definitive notebooks for almost all intents and purposes. They have become synonymous with notebooks themselves since they cater to such a wide audience. Not only is there a variety of different notebooks, calendars, planners, etc... available, but they are produced with high quality materials. They are often regarded as being the first choice for many creative professionals. The only true drawback is their price point which is often at the high range of the market.
Gridbooks For designers, by designers. Gridbooks offers a small yet considered selection of notebooks featuring carefully designed grid systems catering to a variety of designers from print to web. If you're looking for a new way to quickly sketch web layouts based on multiple different grid systems, Gridbooks might have just the notebook for you. But the pages aren't limited to just grids. There is also ample room for annotations to the designs as well as other general notes.
Field Notes These notebooks are very affordable and cater to the craftier, home-grown audience. Produced in much smaller quantities than Moleskine, Field Notes instead focus on the craft of the book and making smaller notebooks which are meant for the "field" as the name dictates. They're not supposed to contain your hour long sketches or thoughtful dissertation. They should be used when you're down in the trenches of your work and need to record some quick notes on the fly. It's not about being precious with them. It's all about efficiency, speed, and cost-effectiveness. (Image: Flickr member See-ming Lee licensed for use under Creative Commons.)