These pages are simply in alphabetical order, more or less; I wouldn’t presume to rank them according to how useful they are, although I will presume to comment on any areas of specific utility or how useful I found them.
I’m going to start with list of forums which are not in English; I honestly can’t say how useful they’ll be, as I don’t speak any language but English with real fluency, but I know how much help fora in my own language have been, so I mention the possibly-useful here, followed by (mostly) English resources:
Club JaPen - Japanese.
ElitePen - Russian.
Forum Styloplume - French.
Fountain Pen.it - Italian.
Fountainpen-Community – German.
Forum o Piorach - Polish.
Foro de Estilográficas - Spanish. I hope it’s good, because there’s a lamentable amount of pop-up advertising.
Gang Bi Wang – Chinese.
Grafopasión – Spanish (subforum on a photography forum).
Penbbs - Chinese.
Penexchange - German (has an English aspect, but less populated; run by Pelikan)
Pennamania - Italian.
Piora Wieczne – Polish.
Reservoarpennor - Swedish.
* * *
Bill’s Pens - some good reference pages, and he sells PDFs and hard copies of period catalogues, which are very useful for answering “what’s this thing?”
Richard Binder Fountain Pens – Check out the “Reference” page for a vast resource, mainly about US-made pens but certainly not limited to them.
Stephen Brown’s Youtube Presence – loads of reviews, demonstrations, and occasional swords. Entertainment and information all in one.
Calgary Pen Club Database – dimensions of pens, generally with pictures. It’s information I’ve put down in my pages, so it MUST be useful.
Canetas e Coisas - “Pens & Stuff” in Portuguese. For we who don’t speak Portuguese, there’s plenty of pictures, including some dismantling directions that are helpful.
Walter Chang’s Fountain Pens – a collector offering his collection for display. Particularly useful for Waterman spotting.
Chiltonpens.net - Specific to the output of the Chilton company; helpful in chronology and model identification.
Collegium Ars Scribendi - A German pen club, whose site has some useful looks as some of the less available vintage German (and otherwise) makers. They apparently also go on field trips, the lucky pups.
Crónicas Estilográficas – An excellent source of information on Japanese pens, in blog form (so it may take some digging).
Tyler Dahl Pens - blog with loads of instructional videos.
Dave’s Mechanical Pencils – Good for sorting out what’s going on inside those things.
Esterbrook.net – The chief resource for those concerned about this brand’s pens.
Vincent Faticia’s Pens – Another collector showing his goods.
Fountain Pen Community - A forum, somewhat more recently established than the three which follow, but laden with good information.
Fountain Pen Geeks – A forum and news site; lots of visual media by the two chaps in charge who appear to live somewhere with a 37 hour day.
The Fountain Pen Board – A slightly different mix of folks from the Fountain Pen Network (my habitual hang-out), but of very high erudition.
The Fountain Pen Network – A forum for enthusiasts; questions one cannot discover the solution to elsewhere are frequently answered, and more often than not, correctly!
Fountain Pen Network-Philippines – Emulation of the above rather than affiliation.
Goodwriters’s Blog – A good place to look when trying to investigate UK brands.
Grandmia Pens on Youtube – How-to videos.
Ink Nouveau - Goulet Pens’s multi-media experience.
Newton Pens – How-tos in the area of making your own pen very nearly from scratch.
Mabie Todd Pen Listing – a UK source, at the just a catalogue of model numbers and descriptions of the pens they’re attached to; this is more useful than it sounds.
Main Street Pens – offers many useful hints under “Articles and Essays” about making your own tools for repairs, and what to do with them.
Parker51.com – A magnificent example of how finely dissected a single topic can be. Highly recommended, if that’s the pen you’re wondering about.
Parker75.com – Slightly less bulging with information than the previous entry, but similarly focussed.
ParkerPens.net – Extremely specific to make, but not limited to fountain pens. Highly recommended.
Pelikan Collectibles - An excellent overview of the company’s models; there has been contact with Pelikan’s own archives.
Pelikan-Guide – If you think something’s amiss with the site, scroll down. It’s worth it.
The Pelikan’s Perch – Brand specific, currently very focused on the modern Souverän line.
Pen Collect - A Parker-specific site, again, with some very nice pictures.
Pen Collectors of America – You need to pay a membership fee to see the best stuff, but there’s some really useful material archived here.
Pen Economics – A blog that is (relatively) focussed on its name; not interesting to all, but some will be quite interested.
The PENguin - as a source of information, mainly useful for Pelikan history (but rather useful).
Pen Hero – Very good for Sheaffer pens of most eras, rather good generally. Also, excellent pictures.
The Pen Museum – Not a physical place, alas, but worth a look all the same. Some of the repair techniques make my hair stand up a little; think before acting.
Pennibink’s Nath – Primarily focused on a single model of Waterman (the Le Man), but one despises any Waterman information at one’s peril.
Pensbury Manor - Wall to wall Wahls; not a vast amount of text, but a good visual reference.
Pen Shots and Thoughts – the entry of this blog which I link here provides help in sorting out Watermans of the 1970s; sadly, there’s not much else there (yet…).
Penspotters – Good breadth, good depth, but not lately updated.
Pentrace - Forum for and articles by pen enthusiasts; a high general level of scholarship. (There has been a change in who looks after the site; this link should work if the other is producing errors)
Carmen Rivera’s Vanishing Point Page - Very useful, and a little hard to spot at on the home page.
Quarterly Illustrated Vintage Pens – While offered as a sales catalogue, it is a useful reference to help sort out model names and dates.
Ryojusen Pens – Japanese makers (so some pens produced in other parts of Asia also figure in).
SGFountainpens - Singapore; it’s in English, but is sort of regional in focus.
Sheaffer Flattops - Also very good for desk sets.
SheafferTarga.com – Information is also available about many other inlaid-point Sheaffers.
Sproctor’s Lamy Pages – as good a source on that pen maker as I know.
Stylophiles Online – a magazine site, a little more academic than many of my links, and aimed a little more at the capital C Collector than otherwise.
Tokyo Fountain Pen Scene – a good reference for Japanese pens and a quantity of information about pen collecting in Japan.
Jonathan Velley’s Mechanical Pencil Museum – yes, I know it’s not pens.
W-B Pen and Watch – Lots of useful information on obscure makers; you can also buy pens and watches from them.
Werner’s Info Page - Pelikan central. Auch auf Deutsch.
The Writing Equipment Society - useful mainly for those in the UK, as their archives are mainly physical; a mere tantalization to the rest of us.
The Vintage Pens Website – some extremely useful articles in the archive.
Watchuseek - a subforum on a watch forum, said to be Dutch but all the text is in English
Waterman Kirkel - A German brand-enthusiast’s site. Not a huge amount of data, but pictures are helpful in sorting out models and as I point out above, one cannot overlook any Waterman reference material.