This website is more like a helper forum, it has an incredible amount of karate moves and many users which explain how to properly do them. Of course you should already know something about karate to attempt them.
This websites offers some truly useful self defense items, of course before purchasing you should make sure that what you buy is legal in the state/country you reside as they all have different legislation on the matter regarding the item themselves or at lest the maximum power they can have (like stun guns and the like).
This is in my opinion one of the best self defense accessory site that there is. They have some really high end things, some a bit expensive, but definitely worth the price. You can never be cheap when purchasing something which could save your life one day.
They have everything from stun guns to blow guns to child safety to diversion safes. Also has things for home protection and strict personal protection. This is probably the most complete site that there is.
This in my opinion is more for kids than anything, especially given the prices of these sound receivers, none the less the site does offer some pretty cheap items to see wether or not your phone is being tapped. Helps protect your privacy.
More than anything this is a fun gadget site that offers kids the possibility to feel like a spy. The gadgets are quite cheap and provide hours of fun.
This is for a more heads on approach. Keep in mind that in some states and countries brass knuckles are considered illegal, regardless of any weapon permit you might have. Make sure to check your local laws before purchase. There are many other items which seem much more powerful on this site than many other.
This is the extreme version of what a car alarm could be. Read the story, it is truly incredible the lengths people would go to to protect their things.
Simple Knife Defense