Lido Key offers the closest beaches to downtown Sarasota, and is home to the world-famous St. Armand's Circle, an upscale shopping and arts district just blocks from the beach. It follows the same pattern that most of Florida's barrier islands do: hotels on the beach, residential areas on most of the rest of the island.
The north and south ends of the island are both public parks, with the beaches on the north end being the best beaches for those who prefer quiet.
One of the most famous attractions on Lido Key is Mote Marine Laboratory and Aquarium, a scientific research and education center that combines marine biology with education. You want to see live sharks and rays close up? Mote Aquarium is the place. It takes at least half a day to see it all, more if you're really into that sort of thing. If you have kids, you have to take them to see it.
As far as the beaches go, they are excellent. The sand is white and soft, the water is clear and calm and shallow, and there are three excellent public beach accesses. The best swimming is at North Lido beach and at Lido Public Beach (about mid-island). South Lido Park is great for picnics, fishing, and sunbathing, but you should avoid swimming there because of strong currents in the pass which affect the adjacent beaches.
Accommodations:You'll find several excellent hotels right on the beach as well as some old-Florida style motels near the beach. The bigger hotels are the Lido Beach Resort, the Holiday Inn Lido Beach, and the Helmsley Sandcastle. If you're staying at least a week, a rental condominium might be more suitable. Nearby beaches are Longboat Key to the north and Siesta Key to the south.
You can drive directly from Longboat Key to Lido Key, but to get from Lido to Siesta you'll need to drive through Sarasota. It's not far, but traffic can be congested, especially during the winter and spring months.
A well traveled trail on North Lido Beach. There is a very wide dune field on North Lido which attracts discreet (mostly) nude and thong-clad sunbathers who are looking for privacy. Nudity is officially prohibited. North Lido attracts a higher percentage of gay sun worshippers than other nearby beaches, but the beach is enjoyed by everyone. All are welcome. The tall Australian pines you see mark the location of a semi-wooded park which can be acccessed from this trail. However ther is no parking provided for cars, so you can't drive to it. There is no parking allowed on the neighborhood streets.