You can't do something you do not know... as good as Grampa Dans advice is, if you are on the low end of the design curve, designing something with no idea of process or basics may not have the best results, you have to crawl before you can walk... natures law, not mine.
It's already obvious that you have some inspirational material by looking at Letterhead fonts gallery, Joe Diaz's work and Imagination Corporation... but at some point, these men were inspired by others... who? that is for them to say.
One guy once came on here saying it was hard to find a good sign design book.... at the low end i would agree, but on the high end, there are thousands of books.
The problem I see is you may not know all your competition, there are hundreds of designers in your general area who can design as well as the people you named, you may not be their competition, so when you raise the bar, your competition is also raised.
One thematic books, one I highly recommend is:
"Walt Disney Imagineering: A Behind the Dreams Look at Making the Magic Real" they just released a revised version and I suggest that one. Lots of sketches and stories.
There are quite a few environmental graphics books too....
Designing and Planning Environmental Graphics-Wayne Hunt,Gerry Rosentswieg
Urban Entertainment Graphics: Theme Parks & Entertainment Environments-Wayne Hunt
Environmental Graphics: Projects & Process: Projects & Process-Wayne Hunt
I also purchase Pixars "Making of" books, they discuss the process of the movie and sketches and helps get into the mind of how they work...
On logo design:
LogoLounge Series Volumes 1-5
LogoLounge Master Library Volume 1 (Volume 2 coming out soon)
Logo Design for Small Business
Logo Design for Small Business 2
Design Matters: Logos 01: An Essential Primer for Today's Competitive Market (v. 1)
Logo Design Workbook: A Hands-On Guide to Creating Logos
Letterhead and Logo Design 9
Letterhead and Logo Design 10
Letterhead and Logo Design 11
Logo Lab
The Secret Life of Logos: Behind the Design of 80 Great Logos
a good site to learn step by step is: (he also has a nice book coming out soon)
http://www.illustrationclass.com/
There is a process for design, most of these books explain it, or tell the story of how the designers came up with the design, start by learning the process. Practice will make you better... being curious can make you great.