Weapons
BOMBS & EXPLOSIVES
How Bombs Work
http://science.howstuffworks.com/bomb.htm
An overview of not only how bombs work, but links to how other explosives work, such as grenades, landmines, C-4, dynamite, nuclear bombs, dirty bombs, and more
Types of Explosives
http://www.nctc.gov/site/technical/common_explosives.html
A brief overview of types of explosives from the U.S. Counterterrorism Center
FIREARMS & BALLISTICS
Adam Firestone
http://adamfirestoneconsultant.blogspot.com/
Weapons advice and consultation from an aptly named Army veteran and weapons instructor.
Bullet Basics: Materials
http://www.firearmsid.com/bullets/bullet1.htm
Types of bullets and casings.
Firearm Calibers
http://www.gunsandcrime.org/caliber.html
A brief, but helpful overview of calibers
Firearms ID.com
http://www.firearmsid.com
How to identify various types of firearms and bullets, with photos and illustrations
Firearms Identification and Ballistics
http://www.drtomoconnor.com/3210/3210lect05a.htm
Includes an overview, history, basic information for those who know virtually nothing about guns, and links to more information
Firearms Technical
http://www.firearmstactical.com/tactical.htm
Lots of articles and briefs, including wound ballistics
Firearms, Tools, Toolmarks, Serial Restoration
http://michigan.gov/msp/