There are a large number of fine Napoleonic websites. Here is a list of less than a dozen. They were selected on the criteria of permanence and either wider coverage or greater depth than usual.
The Napoleon Series - If you're interested in Napoleonics you should bookmark this one. Actually you probably already have.
NapoleonGames.Com - The Operational Studies Group has produced the best Napoleonic boardgames around for a long time now.
The Nafziger Collection - Most extensive and authoritive source for Orders of Battles that I'm aware of. He charges, but the fees are very reasonable. Now with new URL and much prettier site.
GreenHill Books - A major publisher of military history. Often reprints classics in military history.
Web-Grognards - Long-standing and extensive website on wargaming maintained by Alan Poulter.
War Times Journal Archives - Online access to some selected primary sources