Thanks to one of the links in comments, I've got a good run through Kellogg's and General Mills cereals. Another link might, or might not, give me the rest- the only place serving volume is given is in a drop-down menu, and I'm not at all certain I trust it.
Anyway, what I've got so far is here:
http://www.wlpcomics.com/lj/cerealstudy.xlsWhat I'm finding is, at least of the Kellogg's and General Mills cereal lines, the calorie density per gram isn't too far off a uniform set- 40g runs an average of about 160 calories, with only a couple of exceptions. The lowball winner in what I've got so far on this is a tie between Fiber One and Mueslix- the latter of which I haven't seen on a store shelf around here in quite some time.
But, again, we don't eat cereal by weight, we eat it by volume- and that means some cereals you'd think were healthy turn out to be, when you fill up the bowl, quite the calorie bombs.
The big loser so far, in a 12 oz. bowl, is Wheat Chex- 320 calories per bowl. WHAM! Raisin Bran and Raisin Bran Crunch- each at 285 calories per bowl. SOCKO!
The lowball five cereals so far on calories per bowl are:
#5: (tie) Multi Grain Chex and Multi Grain Cheerios, each at 165 calories/bowl, 153 calories/40g. (NOT at all fond of Cheerios in any form, though I'll eat Honey Nut; haven't tried Multi Grain Chex that I can recall.)
#4: Froot Loops, 165 calories/bowl, 137.5 calories per 40g. (Hm. Need to look around and see if there's a Reduced Sugar sold in the local stores.)
#3: Rice Chex, 150 calories/bowl, 148 calories per 40g. (Rather like them, but prefer Wheat Chex, alas.)
#2: Kellogg's Corn Flakes, 150 calories/bowl, 143 calories per 40g. (Blech.)
#1: Kix, at only 132 calories per bowl and a calorie density of 146 2/3 per 40g of cereal. (I kind of like this, but the rough corn puffs abrade the roof of my mouth, so I don't eat them much. Same problem with Trix.)
Thanks for your help so far, and please keep forwarding me info if you have it. Quaker (including Capn' Crunch side brands) and Post are the main companies I'm still looking for. Not much interested in Malt-o-Meal, which last I looked is generic bulk knockoffs of the brand name stuff.