Until their discovery by (mostly) California chefs in the late 80s, early 90s, Meyer Lemons seemed almost not to exist unless you were among the probably thousands of Bay Area residents with a tree in your back yard.
Fast forward and they've practically reached the point of ubiquity—but not quite, because they are soooo good and I still get excited when I see them for the first time every winter.
They have gorgeous, golden yellow rinds that, when rubbed gently, give off an intensely floral perfume. Inside, the lemons are tart, but they have a sweetness and complexity that regular Eureka lemons lack. They're generally not waxed, so the rind is much nicer for desserts, salad dressings and gremolata.
You can use Meyer lemons anywhere you use regular lemons with great results. Think tarts, pound cake with lemon syrup, pots du crème, salad dressing and lemonade.
One of my favorite things to do with Meyer lemons is to make a bed for halibut or other mild, white fish. Just slice thinly, rind and all, and place a single layer in a baking pan, drizzle with olive oil, add herbs, top with a fillet of fish and roast in a 400° F oven for about 10 minutes (depending on the thickness of the fish). The lemons release their distinctive flavor when heated.
Here's an entry from last winter on Cooking with Amy with some tasty ideas. Capay at the Noe Valley Farmers' Market, had them for the first time on Saturday, so the season (which runs well into spring) is just getting into swing.