The number of sites devoted to pens is now huge. Some useful sites are maintained by clubs and are listed under that heading. Most sites, however, belong to individual pen enthusiasts, and as one might expect, are a somewhat mixed bag. Many are primarily sales listings; historical information, when included, is often taken from other sources. There are sites that are truly useful references, however, such as the ones listed below:
Internet Pen Resources: Craig Lewis has been compiling encyclopedic lists of pen resources online for some time, and now Tamer Oszu has put them on his website.
Tony Fischier's Parker site: A vast compilation of material on Parker pens, regularly updated and expanded.
The Leadhead's Pencil Blog: Jon Veley is an indefatiguable collector and researcher of mechanical pencils. His site is a treasure trove of information, much based upon original research.
Bill Acker's: Thumbnail histories of selected pen companies, pictures, pen show information, links.