I know that most shops arn't going to have everything you like. But on average which ones have what you need when you need it, or can get you what you need in a short time.

www.anticsonline.co.uk is has a nice selection of models, paints, scenics etc. Don't know if they ship to the US though.

Squadron Shop does a good job, although I have had some problems with lost orders and wrong items in the past. But that seems to be improved in the last year or so.
I use Mission Models for Resin kits, ect. John has found things for me that I couldn't find anywhere else.
Sometimes it takes a while, but he has about a 95% success rate in my case.
Chuck

"Gav" at panther models hasnt let me down yet !
and "Lee" at military precision
boh have great stock and usually ships really quickly plus just about the best price in the u.k.

None!!
That's why I always have 4-6 bookmarked.I am also eternally poverty stricken in the hobby budget :-) I never order just one item. Resin figs and foreign(non US) odd stuff I can always count on R&J productions.All have their strong/weak points.
cheers!
Rick

Mission Models.

discountmodel.com here...... Mark's a great guy... and so is Gordon @ Sprue Bro's