I want to acquire an AR15 type rifle. I have and use several bolt action centerfire and rimfire rifles, and pistols, but this would be my first AR. I've got an AK47 for "play", and am interested in a self-defense/trunk gun/target shooting weapon. I'd appreciate some input on which manufacturer, which model and who to buy from ...online source, etc.  Thanks.

You cannot buy an AR-15 online-
You must be a Federally Licensed Firearms Dealer

When you find one that you like for sale you must have your licensed dealer send the liscensed dealer who has the rifle you are interested in a copy of his license..

The dealer can then send the rifle to your dealer who will record the sale in his bound book.

You then must purchase the weapon from him according to the applicable state laws..subject to a law enforcement background check and waiting periods in accordance with your state requirments.

There are several licensed dealers and manufacturers who advertise on this board.
There is also an Equipment Exchange Forum under board list in the header...

Good names to look for are (in no particular order) Armalite, Bushmaster, Colt , Rock River, DPMS , Les Baer, Wilson, Fulton Armory..there are more but this will get you started..
For a more custom rifle..check out
Kurts Kustom Firearms under the industry header...here you will also find some of the manufacturers and dealers...
Good luck..you've picked an interesting time in our nation's history to buy one of its most famous battle tools....