Historical Maritime Society - Royal Navy reenactment and research group. Good looking site marred by tinny background music that you can't turn off.The Royal Navy during the Napoleonic Era - Describes the ships and men of the Royal Navy 1793-1815.
The Manoeuvrability of Warships in the Napoleonic Period - An ongoing investigtion into the time taken by sailing warships to tack and to wear.
Nelson and the Nile - Article describing the Battle of the Nile and the events that led up to it.
HMS Victory - Pictures, history and virtual tour of Nelson's famous flagship.
Bravé - Dedicated to the French navy and its allies during the period, this site promises a lot but delivers very little. There is a discussion forum and some links to follow, but otherwise very little content.
Wargaming the Age of Fighting Sail - Not (exclusively) a wargaming site, but a comprehensive selection of naval, wargaming and modelling links.
The Trafalgar Roll - Part of a genealogy site, this page lists British ships and seamen (some 1,640 of them) who fought at Trafalgar. There's also lists of killed and wounded and brief descriptions of some other naval actions.
Broadside - Describes life in Royal Navy in the late eighteenth and early nineteenth century.
The Russian Navy in the Coalition Wars - Page that describes Russian naval activity during the period, part of an on-line history of the Russian navy.
Naval History: Great Britain. - Collection of on-line documents written between 1801 and 1820.
Battle of Cape St. Vincent - Site created to mark the 200th anniversary of the battle. Account of the action and details of the British commanders.
Count VerHuell (1764-1845) - Biography of this dutch admiral, the only dutchman with his name on the Arc de Triomphe.
French Ships of the Line 1793-1815 - A list of French ships active or under construction during this period. Includes the battles/campaigns in which they served and other historical details for each vessel.
List of Ships of War, which were lying in the Tagus, 1806. - The Portuguese fleet, as observed by Lord St Vincent.
The Battle of the Saintes - Not strictly a Napoleonic battle, but one that set the style of naval warfare for Nelson and others to follow.
Admiral Lord Duncan - Biography of Adam Duncan, victor of Camperdown in 1797.
Navies in the Age of Nelson - Collection of documents and eye witness accounts of the war at sea, in both the Napoleonic Wars and the War of 1812.
Battle of Trafalgar - Lengthy account of the campaign an battle, from a site dedicated to HMS Victory.
The Battle of Trafalgar - Article on this decisive naval battle from about.com.