Arms and Armor v3.5 is a collection of additional, well, arms & armor for use with d20. It is an updated version, taking advantage of newer 3.5 rules.
From the publisher:
"Weapons and armor are the pulse behind every campaign. Every slash of a blade, crash of a hammer, and whistle of an arrow is an orchestral testament to life and death in the harsh adventuring world. Armor serves as a chronicle, recording every critical blow and explosive spell. Heroes and villains alike are molded by the weapons they wield and the armor that protects them. Within Arms & Armor v3.5, you’ll find:
• More than 200 weapons
• Nearly 200 unique weapon qualities
• More than 100 kinds of armor
• Nearly 200 unique armor qualities
• New rules for Artifacts and Legendary Weapons
• Open Content culled from more than 100 sources
• And More!
Arms & Armor v3.5 is more then just an update to Bastion Press' original 3.0 release. This book contains all the weapons and armor you’ll need for your campaign, each carefully updated to v3.5 and balanced for easy use in any campaign. New artwork, monsters, weapons, and armor are waiting to rock your world."