Wow. Nobody mentioned ANYTHING else but Kona! It's clearly a landslide vote!
They do, by far, have the widest range of colors, though there still are colors I'm looking for that they don't have.
Have any of you tried RJR's Cotton Supreme? I don't know if it's quite as beefy as the Kona... but it's a little softer to the touch. I prefer the RJR black over the Kona black, 'cause the RJR does not develop as much of a "shine" during ironing. As to the whole "shine" issue, I found that Springs Quilters Only solids didn't "shine up" at all. Moot point now, as Springs is not making that line anymore. (Well, maybe they will do some just for JoAnn's...)