Linkyard

Common Lisp

http://www.gigamonkeys.com/book/
Practical Common Lisp - awesome free online version of a book for learning Common Lisp
http://www.lispworks.com/documentation/HyperSpec/Front/index.htm
Common Lisp HyperSpec - a language documentation
http://lispgames.org
Lisp gamedev resources
Delivering games written in Common Lisp
Guide to shipping Common Lisp applications while avoiding most annoying problems

Math

A Beginners Guide to Dual-Quaternionscopy
What they are, how they work, and how to use them for 3D character hierarchies
Dual-Quaternionscopy
From classical mechanics to computer graphics and beyond

Bikes

http://forum.velomania.ru [RU]
Отличный ресурс для общения на велосипедную тематику. Организация велопоходов, велопрогулок.
http://kotovski.net [RU]
Очень полезный блог для начинающих велосипедистов (продолжающим тоже будет интересно)

Gaming

http://whitesideridge.com
Whiteside Ridge server community of Guild Wars 2