I'd like to offer some humble opinions as food for thought. Please don't think any of this is intended to sound "preachy" or like I think I'm a know-it-all, because it's not intended that way.
Linking up with
trustworthy friends is a great idea, but I wouldn't trust strangers with any information I wouldn't want the pork to know about. Without having some reliable method of lie detection, or at least a thorough background investigation process, any militia organization will be thoroughly infiltrated by feds before it gets a chance to do anything. Even with such safeguards in place it probably won't be possible to keep out all spies or informants indefinitely. Small groups of close friends are probably the way to go. If it becomes necessary to fight against naked tyranny, everyone will know who the enemy is, and independent cells will be able to plan actions accordingly.
Also, I think many folks (not necessarily anyone here) who are affiliated with militia groups are very well-intentioned but have the wrong idea about how to successfully resist a modern tyrant's forces. Basically, just about anything a conventional military force would do is wrong for that purpose. You don't use "fire and maneuver" when you're outnumbered and outgunned. You use "hit and run," preferably via sniping or IED attack. The stealthier, the better. Ideally, the enemy should never even get a chance to return fire before you've disappeared.
Even a suppressed handgun in .45 ACP, if used cleverly, can be a valuable weapon against modern forces of oppression. As someone once said, the 21st Century militiaman might do better to imitate Agent 007 as opposed to John Rambo. Use of rapid-fire assault rifles should be a last resort, when you're already surrounded and are just trying to take a few of the bastards with you.
These are the kinds of skills I think we should be emphasizing in case we need to resist a modern military force via asymmetrical warfare:
Physical fitness. FAR too many militia people neglect this. Everyone should be capable of meeting
at least the military standards for his age group. Those who are physically disabled (bad arthritis, etc.) can still play important roles in a resistance (making weapons, etc.), but they shouldn't be doing the "dirty work" unless there's no alternative.
Marksmanship, especially long range. Being able to hit a man-sized target at 500 yards is nowhere near good enough, since the target will probably be wearing body armor and a helmet that can stop your bullet. You need to be able to hit a face or a pelvis at 500 yards or more. Get yourself a bolt rifle that shoots better than 1 MOA and has a nice, high-powered scope. If money is a problem, the Super Sniper scopes are a real bargain at ~$400. They can withstand even .50 BMG recoil better than many far more expensive scopes.
How to make firearm suppressors. These are important for stealth work because of the increasing use of acoustic gunshot detection systems. The Silencersmithing forum here is a good place to start:
http://www.silencertalk.com/forum/index.php
How to reload, especially subsonic rounds.
How to manufacture AP bullets from monolithic solid bullets. This requires a small lathe.
How to make and use IEDs. There are plenty of books and online materials (including on YouTube) that can provide info on where to get chemicals and how to make high explosives. Note that there's no need to actually do anything illegal if you don't want to at this point; just
learn about the stuff so you can do it if you have to someday. Save the info you collect in a secure place.
Some examples of good websites on this topic:
http://www.powerlabs.org/chemlabs/index.html
http://stupid939.tripod.com/id25.html
http://flashbangboom.homestead.com/procedures.html
Forensics. Do you know about gunshot detection systems, DNA testing, face recognition systems, automatic license plate readers, etc.? Did you know that microscopic corrosion from where you touched that bullet jacket can be made into a fingerprint? If not, start reading up and thinking about countermeasures!
On a final note, two books I highly,
highly,
HIGHLY recommend are
Fry The Brain: The Art of Urban Sniping by John West
The Ultimate Sniper by Maj. John Plaster