A few other folks who wrote in about places to paddle in Florida:
Baffinpaddler noted that she too had tried a mangrove trail and found it claustrophobic. The trails can be tight, though it's also true that not all mangrove trails are the same size. The first part of the Woolverton in Placida was quite narrow, but the trail from the lagoon back to the bay was wider, as were the trails in Sanibel. She recommended paddling in Cockroach Bay, near Tampa. She's paddled there with Big D's Kayaks
Cockroach Bay, Tampa Bay Florida - Kayaking with Dolphins and Manatees
Mangroves, Caladesi Island, Barrier Islands, Tampa Bay Florida
Rob Allen, Kayaking Michigen was also recently in Florida: He went on a Mangrove Tour in Palmetto and on the Little Manatee River in Wimauma
Sarah of Sarah's Soggy Scenarios recommended paddling in the Everglades. I didn't see any posts for those paddles on her blog, but I did find that Places We've Kayaked had a post about renting kayaks in the Everglades.
I also wanted to mention a few places we've gone to on prior trips. Just before Thanksgiving 2003, we rented kayaks and canoes from Canoe Escape and paddled on the Hillsborough River, east of Tampa. It was a wonderful trip for spotting ibis, herons, vultures and especially alligators.
In 2009, in addition to paddling at King's Bay, we rented kayaks from Riversport Kayaks to explore the Homosassa River, home to an island of monkeys.
But of all our rentals and trips, the best has been the Ozello Paddle with Aardvark's Florida Kayak Company. It is rare to have such wonderful gear and such a talented guide.
Then there are those kayakers lucky enough to bring their own boats to Florida including:
Dave's Yak Tales: He lives in Florida and is out paddling regularly
Sea Kayak Stonington who paddled the length of the Keys in 2011 and the Everglades in 2010
Finally a guide to Florida: Paddlers Guide to the Sunshine State, by Sandy Huff, 200, University Press of Florida. We used this in 2009, but did not pack it this time, since it does not cover Sanibel Island.