I've always maintained that Field Gulls has the best X's and O's analysis on the web. But if Field Gulls ranks number 1 in that department, the Redskins' site (Hogs Haven) is a very strong 1A.
In particular -- but only if you don't mind getting hooked and spending an hour or three -- check out this index to the complete set of film analyses done by a Hogs Haven regular, UKRedskin. Basically, they're in-depth film looks at the Redskins' players, plays, and formations, including (of course) their version of the read-option. You'll also find a recurring complaint that's familiar to all of us here, but which the national media never seems to appreciate: "WE'RE MORE THAN JUST A READ-OPTION TEAM!"
Of course, the Skins' offense with Robert Griffin III isn't the same as the Seahawks', but both offenses are interesting to watch, and it's instructive to observe in depth some of those differences. Add in the possibility that we might face Washington again in the playoffs, and that makes this series definitely worth a visit.