The following are links that collectors looking through these pages might well find interesting or even invaluable.

General interest
http://www.forumancientcoins.com/board/index.php - A great numismatic forum for the new and experienced alike.
http://www.ancients.info/ - A site containing a forum of knowledgable collectors and dealers.
http://bpmurphy.ancients.info/ - Illustrating some of the collections of Barry Murphy
http://dougsmith.ancients.info/ - Doug has a wide range of articles of interest to the novice through to the experianced collector alike.
http://www.beastcoins.com/toc.htm - A fascinating site with several areas of interest.

Probus
http://probvs.net/ - The best Probus site on the net. An invaluable resource for the Probus collector.

Septimius Severus
http://bpmurphy.ancients.info/severan/severanhome.htm - The net home of the Barry Murphy collection of Severan denarii. Barry has kindly consented to me using many of his images from this site on my own Severan section.
http://dougsmith.ancients.info/severus.html - The Doug Smith collection of Severan denarii.