Nick,
I got onto the low-tannin/edible acorn oak bandwagon 15 years or so ago, and still dabble around with 'em some, though I've concentrated more on northern pecan/hickory and persimmon in recent years.

Ken Asmus at OIKOS is probably one of the principal purveyors of 'edible acorn oaks', and I've got a number of his offerings growing here; some in the ground long enough to be producing reasonable crops of acorns.

Don Cobb, who's the Northern Nut Growers Assn. Edible Oaks committee chair has had acorns, seedlings, and scionwood available from time to time - and he gifted me with acorns from some of his low-tannin Q.bicolor & Q.macrocarpa selections several years ago.
My taste evaluations of some of Don's Q.bicolor selections leads me to believe that pure genetics are not the full story on 'sweetness' of white oak group acorns. The 2000 or 2001 crop of Don's "Cobb Sweetie #2' bicolor were very non-bitter - sort of like eating a very bland chestnut - not much flavor, but no bitterness; but the next year's crop was indistinguishable from any other white oak acorn I'd sampled - there was typical bitterness and astringency. So...I suspect that rainfall, growing degree days, etc. may play a significant role in the 'sweetness' of acorns from year to year.
You might check the NNGA website for more info, and check out the International Oak Society webpage - some members there also have an interest in edible-acorn oaks, and there's usually an 'acorn swap' conducted at the yearly IOS colloquium, wherever it's held.

While the native Americans did utilize acorns from the white oak group, it seems that members of the red oak group were often preferred - they 'store' better, have higher fat content; the tannins are somewhat different between the two groups, but both must be leached out.
A friend who makes acorn meal/bread, etc. has indicated that once the white oak acorns sprout, the tannins are 'fixed' and you can't effectively leach them out of the acorn.

There are several books on preparation of acorns and usage by native Americans - one of the best is "It Will Live Forever, Traditional Yosemite Indian Acorn Preparation" by Beverly Ortiz, as told by Julia Parker. A very interesting read.
Another one, with plenty of recipes, is "Acorns and Eat 'em", by Suellen Ocean.