Every NRA member has $1000 worth of free firearms insurance, then it's $16.67 per additional $1000. I'm fully insured through them and never had a claim (thankfully), but the terms / conditions seem very reasonable.
The insurance provider is actually Lockton Risk in Kansas City. They're well known in the cellular phone insurance trade and a fairly respectable company.
Some things I've ran into with them is if you submit a request for additional insurance, it's takes about 4 weeks to receive a reply via snail mail with an updated policy. They will have you covered as soon as they get your request, but don't expect a new policy in your hands quickly.
Also, some folks think the free $1000 insurance will be paid "in addition" to whatever their homeowner's policy might cover. This is not true. You either fully insure your guns through your homeowner's policy... or through the NRA... and make a single claim through one or the other... but not both.