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.
Histoire et Figurines - Parts are French only, but if you're interested in Napoleonics you must visit this site. It covers the entire period in fair depth. Very nicely done.
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.
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