Florida Memory, the site of the Florida State Archives, has
added a database of Floridians (those from Florida or those
who entered the service in Florida) who served in World War I.

It's available at

http://www.floridamemory.com/Collections/WWI/ . Since
42,000 Floridians served in WWI, this collection is pretty
extensive.

You can search this collection by name, branch served,
serial number, rank, race, city, and state/country of birth.
Search results come in a table that shows branch of service,
rank, service number, race, name, birth city and
state/country, and city/state of residence. Click on the
name and you'll a digitized version of the service card.
Information varies between cards (because different services
recorded different information) but generally you can get
dates of service, rank, and place of service in addition to
the information available in the search results. A printer- friendly
option shows the card on a page by itself.

If you don't want to search, you can also browse this
collection. The browsing page has the count of each service
branch in this collection (from the Army with 36,254 cards
to the Coast Guard with 221) and links to browse each
service's cards alphabetically.