The websites for The Florida Center for Instructional Technology and The State University Libraries of Florida both provide an large number of historical maps. The Florida State Archives and other local archives provide access to maps at their physical locations.
The Florida Center for Instructional Technology provides approximately 6,000 historic and contemporary maps, all available online. From the main page of FCIT.USF.edu, click on the Florida Maps link near the center of the page. The maps page sorts maps by category, from maps of the entire state to highly detailed maps covering areas smaller than one county. Maps are available in many formats, including JPG, PDF and a special Zoomify version for online viewing.
The State University Libraries catalog at DigiTool.FCLA.edu also provides detailed maps, mostly in the form of high-resolution JPG files. From the main page, click All Collections. Scroll down, and click the Florida Map Collection link. Each map link lists information such as size and date, along with a link to the full-resolution map.
The Florida State Archives has an extensive collection of historical and contemporary maps, which is available in person at the archives. The collection can be searched online using the library's catalogue at FSLT.Sirsi.net. Use the Advanced Search feature to narrow results.