The Internet has revolutionized access to firearms knowledge. On-line research was an instrumental part of my own journey to becoming a gun owner. The following links are far from comprehensive.

Regardless of its constitutionality, the Bureau of Alcohol, Tobacco, Firearms, and Explosives is the federal law-enforcement agency responsible for regulating firearms in the United States.
CalGuns is the “California firearms owner’s home on the Internet.” It is certainly a place for Californians to gather information and discuss firearms.
The Cornered Cat
The Cornered Cat is Kathy Jackson’s site about women and guns. Though intended for women, more than a few men could benefit from its wisdom.
The Firing Line
The Firing Line is an excellent on-line discussion forum for firearms.
GunCite features many facts, figures, quotes, and analysis on “gun control.”
Gun Facts
Gun Facts is Guy Smith’s e-book that lays out well-cited statistics on firearms and crime.
Keep and Bear Arms
Keep and Bear Arms is a website “about helping lawful people maintain their abilities to protect themselves and the people they love effectively … through legal, private ownership and use of guns.”
Information & Discussion

A vast amount of legal, historical, technical, philosophical, statistical, and political information on firearms is available via the Internet. Many websites also include lively discussion forums.
CalGuns Foundation
The CalGuns Foundation is a new leader in the right-to-arms movement, both in and out of California, and it’s getting results.
California Rifle & Pistol
The California Rifle & Pistol Association defends the right to keep and bear arms and promotes responsible firearms ownership in California.
                            Owners of America
Quoting Rep. Ron Paul, the Gun Owners of America bills itself as the “only no-compromise gun lobby in Washington.”
National Rifle Association
In addition to promoting marksmanship, firearms safety, and the shooting sports, the National Rifle Association defends the right to arms in the U.S.
                          Amendment Foundation
The Second Amendment Foundation is dedicated to promoting a better understanding of our right to keep and bear arms. The SAF sponsored the landmark Heller and McDonald cases.
Right to Bear Arms

There are many local and national organizations working to protect and restore the right to arms in the United States. Though usually not as well funded or as well organized as their opposition, these groups have the active support of millions of individual members.
Brady Campaign
The Brady Campaign to Prevent Gun Violence works “to enact and enforce sensible gun laws.”
Coalition to Stop Gun Violence
The Coalition to Stop Gun Violence “pushes a progressive agenda to reduce firearm death and injury.”
Democratic Party
Though not specifically a gun-control  organization, the Democratic Party has been the primary author of the most restrictive firearms legislation in the United States.
The International Action Network on Small Arms advocates “stronger regulation on guns in society and better controls on arms exports.”
Republican Party
The Republican Party nominally supports the right to keep and bear arms for recreation and self-defense, but it has done little more than slow the suppression of that right. In fact, Republican leadership has dramatically failed to push for gun-control reform, even when the need is most apparent.
Violence Policy Center
Approaching “gun violence” as a public-health issue, the Violence Policy Center advocates “that firearms be subject to health and safety standards like those that apply to virtually all other consumer products,” which, of course, they already are.
Firearms Prohibition

Operating under the attractive but arguably false notion that limiting the availability of firearms would reduce suicide, homicide, and other violent crime, a number of well-funded organizations support or actively pursue stronger “gun control” in the United States and abroad. These organizations enjoy widespread support from the academic community and the entertainment media, but their individual memberships are often very small.
AIM Surplus
AIM Surplus is a distributor of new and used firearms. They will also sell directly to licensed collectors.
Yes, Amazon sells firearms accessories (and just about everything else). So far, I’ve still only used it to buy books on firearms.
Ammunition to Go
Ammunition to Go has a good inventory, including ammunition affordably packaged for law-enforcement sales.
Brownells is a major supplier of gunsmithing tools and firearm parts and accessories. Discounts are available to licensed dealers and collectors.
Cabela’s is a major retailer of outdoor clothing and gear, including many firearms-related products.
Century International Arms
Century International Arms is one of the major importers of surplus firearms but will also sell to individual dealers and collectors.
Civilian Marksmanship Program
The Civilian Marksmanship Program promotes marksmanship in the United States and also sells U.S. surplus firearms to eligible individuals.
Empire Arms
Empire Arms is an exclusively on-line dealer of collectible firearms.
Firearms Training Associates
Firearms Training Associates is an instructional organization based in southern California.
GunBroker is an on-line auction site for firearms and other items. It is a great place to look for rare and unusual guns.
Kahr Arms is a manufacturer of superb “compact” handguns. Kahr also provides gunsmithing services and sells parts and accessories.
MidwayUSA is another great source for firearm parts and gunsmithing tools. Discounts are available to licensed dealers and collectors.
Natchez Shooters Supplies
Natchez Shooters Supplies is a great source for ammunition and other shooting supplies.
Numrich Gun Parts
Numrich is a supplier of older and hard-to-find parts and accessories. Discounts are available to FFL holders, but the on-line shopping cart times out rather quickly.
SIG Sauer is the U.S. importer and manufacturer of SIG-Sauer pistols and other firearms. They also have a “pro shop” and offer a variety of gunsmithing services.
Springfield Sporters
Springfield Sporters is an excellent source for antique and reproduction firearm parts.
Products & Services

Many, many firearms-related products and services are available in the United States, but the legal environment often keeps the industry on the far end of the bridge to the 21st century. The listed companies are either leaders in the industry or ones I have done business with.

“Knowing is half the battle.”