Here are some links to sites that I have found particularly helpful

Nibs.com - New fountain pens & nibs, nib customization and repair, fountain pen ink and accessories.

CSV Pens - Conway Stewart Vintage Pens. High quality Pens and Pencils at low prices.

David's Pen & Pencil Collection - Specialises in collecting Conway Stewart Pens and Pencils, plus other writing equipment.

Onoto Pen Company - Luxury limited edition fountain pens and writing accessories made in Britain since 1905.

Pens & Collectables - An extensive range of Fountain Pens, Pencils and Accessories, all fully serviced and guaranteed.

Sheaffer Targa Web Site - Specialist retailers focing opn Sheaffer Targa fountain pens and other Sheaffer models.

Writetime - several makes of vintage fountain pens and pencils, restored to full working order.

The Pen Practice - This site is devoted to the understanding and repair of vintage and classic fountain pens. I am no longer offering a repair service.

Vintage Fountain Pens - a huge collection of fine vintage fountain pen for sale, nibs, spares and associated inkwells, ink bottles and other pen related objects.

Writing Equipment Society - The history of writing equipment and the conservation of both utilitarian and fine items. Aids collectors to add to their collections through sales and exchanges.