East Is East and Easiest Is Best -- A weekend of biking and snacking on the Eastern Shore brought to our attention some important truths: Within sight of the Chesapeake Bay in season it is hard to get a bad crab cake. And if you want anything but crab cakes you might as well stay home. Specifically, we found some good mustard- spiked, sweetly fresh crab cakes at Longfellow's in St. Michael's, which makes a pleasant waterfront alternative to The Crab Claw. In Oxford the Robert Morris Inn makes superlative crab cakes that manage the neat trick of being both creamy and light, just short of melting as you cut into them. On the other hand, The Masthead in Oxford is a newly refurbished and charming little restaurant, with blue candles and tablecloths and colorful wall decorations that look like nautical stained glass. But too- creamy, bland and gelatinous crab mousse was no substitute for a plain old crab cake. The crab-stuffed fish fillets tasted too much of kitchen fussing and not enough of sea freshness, and medallions of lamb were gray, chewy and stewy -- all at big-city prices. It all served to remind us that when in crab-cake country, it's a waste to bother with anything but the plain old tried-and-true local specialty.