http://www.guncite.com/ This is basically an encyclopedia of pro-gun arguments. I like this because I can look up some info to refute a wide variety of anti-gun arguments.
http://gunssavelives.net/ This is a regularly updated list of defensive gun uses in the media. When an anti-gunner sends me a link about some idiot doing something stupid with a gun, I can send him 3 links about people defending themselves and their families.
http://americangunfacts.com/ This is a nice infographic that covers a wide variety of topics.
http://www.a-human-right.com/introduction.html This site by photographer Oleg Volk is great for more open minded people who are relatively neutral.
This article debunks some of the common gun control myths.
Some links refuting the concept that gun ownership is in decline.
On '10 rounds should be enough for anyone':
http://en.wikipedia.org/wiki/On "There are no new gun owners":
Bad guys were hit many times and continued to fight for minutes.
local/ fbi-bullets-used-pittsburgh-pol ice-arent-lacking-s/nXTXT/
"Whatever is keeping some crime suspects fighting after police shoot them five to 10 times, the problem isn't with the ammunition, Pittsburgh police said on Monday."
patrol-issues/articles/ 6199620-Why-one-cop-carries-145 -rounds-of-ammo-on-the-job/
"At the core of his desperate firefight was a murderous attacker who simply would not go down, even though he was shot 14 times with .45-cal. ammunition — six of those hits in supposedly fatal locations."
channel/patrol/articles/2010/ 04/ jacksonville-florida-01-26-2008 .aspx
Police Officer Jared Reston was shot in the face with a .45 and continued to exchange gunfire with the suspect and killed the suspect after being hit by multiple additional rounds. The bad guy was hit seven times and only stopped after receiving multiple head shots.