Here are a few of my favorite Model Railroad related websites.
New Haven Model Railroads
My blog has links to all sorts of sites, but here are a few that aren't hosted on Blogger. 

Peter Ness' New Haven Railroad in 1959.
Peter also helps run the clinics at the NHRHTA Reunion and also does great work...even through his NH 10' IH Postwar Box Car is still missing a few rivets :>)

Kathy Millat in the UK is modeling the New Haven as well and has done some spectacular work.

The Stamford Model Railroad Club is a longtime O-scale club layout founded in 1939(!), with construction of the layout started after WWII in the basement of St. Johns Church in Stamford. 

Bill Schneider's Old Woman in the Back Bedroom (New York, Ontario & Western) from the Internet Archive.

It was an amazing layout in a small space, a lot of fun to operate, and an inspiration for my prior and current layouts. I've actually "known" him for some time, he worked at the hobby store I frequented as a kid, and owned another one I visited when I moved to another part of the state a couple years after I was married...and just before he closed the store. He even recognized me. I finally 'met' him properly at the NE Prototype Meet.

Bill's layout was really the biggest inspiration for my layout and my modeling approach. One of several layouts I operated when designing the layout, and really showed me what you can accomplish (and how) when prototype modeling. As I was continuing to look for a place to model, an old photo of New Britain Yard in front of the station reminded me of of Bill's layout, where a lot of the action takes place in a compact location. 

Historical Information - New Britain
Local History Room at the New Britain Public Library
They have a lot of pictures from the last century, corporate records from the various industries, and the city directories. The directories are similar to a modern day phone book (although not everybody listed has a phone), but they also have tenants listed by street. 

New Britain Industrial Museum
If you're in New Britain, you can visit the museum on Main Street. This is focused on the industries themselves, and the many New Britain inventions (beginning with the coat hanger).

Historical Information - Railroad
The Alphabet Route
This is a great website that covers prototype and modeling information for the Railroads in this agreement - NKP, W&LE, P&WV, WM, RDG, CNJ, L&HR, NH. The site is growing, but it already includes rosters, diagrams, some documents (consist books, etc.) and other useful information.
DOT Investigations of Railroad Accidents 1911-1993
This has reports for all railroads, but you can search for the New Haven. It doesn't have all of them, but there are quite a few.

New Haven Railroad Historical and Technical Association.
The first railroad historical association, and publishers of Shoreliner magazine. The online forum is a must for any fan of the New Haven.

New Haven Railroad Resources
Compiled by the CT DOT. They also have digital copies of the valuation maps. Contact the compiler listed in the report for copies.
Fantastic reference of NYC and subsidiaries freight cars and appropriate models.
The definitive list of PRR freight cars and appropriate models.

Steam Era Freight Cars
A site originally started by Ted Culotta of Speedwitch Media, it is currently managed by another. Updates are very infrequent, but the existing material is must read.