Most of Font Bureau’s Readability Series (designed primarily for newspapers) are graded families:

Benton Modern
Bureau Roman
Miller Daily
Poynter Agate
Poynter Old Style Text
Quiosco
Zócalo Text

Greta Text
http://www.typotheque.com/fonts/greta_text/

Tempera Biblio
http://www.typonine.com/fonts/tempera-biblio/

The Guardian type system by Christian Schwartz and Paul Barnes.

Thank you! I also found this:

Lexicon Roman A
Lexicon Roman B
Lexicon Roman C
Lexicon Roman D
Lexicon Roman E
Lexicon Roman F

Renard No. 1
Renard No. 2
Renard No. 3

Ruse X000
Ruse X010
Ruse X020
Ruse X030
Ruse X040
Ruse X050
Ruse X060
Ruse X070
Ruse X080
Ruse X090
Ruse X100

Some typeface families designed for wayfinding address similar optical issues as Sumner Stone does with his ‘Halo’ fonts, including FF Info, FF Transit, and Clearview Highway. I don’t know whether their metrics are consistent across the variations – which would be a requirement for qualifying as ‘graded’, no?

“[…] each of the six weights of ClearviewHwy are available in a positive contrast version (white type) designated as “W”, and negative contrast version (black type) designated as “B”, and have been tailored by optimizing the stoke widths for the viewing application.” — clearviewhwy.com

“In FF Info the difference between the various weights (Normal, Book, Medium, Semi-Bold and Bold) has been designed to compensate for this effect. For example, white text set in Book weight on a black background is optically the same as black text set in Medium on a white background. With back-lit signs dark text appears thinner, in which case the Semi-Bold weight would be appropriate.” — FontFont

“Front and Back are subtle variations which compensate for the visual distortion that appears on illuminated signs which are either backlit or lit from the front. These variants are also useful for the compensation sometimes required by white text on a black background.” — FontFont

Stumbled across this list while I updated my own one. Like Florian mentions, the consistent metrics across the set of fonts are a requirement for the fonts to qualify as grades. As such, neither the Guardian series, nor Lexicon, Ruse, Info, Transit or Clearview are graded sets in the traditional sense. I’d be curious to find more. Until now my list looks almost identical.

the consistent metrics across the set of fonts are a requirement for the fonts to qualify as grades.

Makes sense*, but does it have to be across the whole set? For example in Clearview, if there are pairs of fonts (a "B" and a "W") that are slightly different weights as well as being uniwidth**, each pair could be said to form a (minimal) graded system, making the typeface as a whole a set of graded fonts.

* Although of course it's not a sufficient condition.
http://typophile.com/node/100708

** BTW, do you think "uniwidth" is a good term?

hhp

It’s hard to tell, but what I was able to see from this image, not all Clearviews looked identical in spacing to me. http://clearviewhwy.com/_images/howItWorks/howItWorks/figure8.gif

Also a set of two fonts would count as grades, sure, see the Stone families.

Ah, you're right - it's not even close. So an interesting question results: can grading not be properly applied to positive versus negative setting of text? Maybe it can only be properly applied to combat inking variance (like at Font Bureau). I wonder because Montalbano (who's known to be technically quite proficient) probably would have liked to make Clearview's "B" and "W" cuts uniwidth, but maybe thought the spacing compromise was too great*; but Stone does regularly shoot for it**. And Hagmann goes all the way.

* Although accommodating halation might have been a special factor in Clearview.

** http://www.stonetypefoundry.com/halofontspage.html

hhp