the-blueprints.com has a searchable database with 37,000+ images spanning twelve categories.
'The-Blueprints.com is a website dedicated to collecting 3/4/5-view drawings, templates and blueprints for as many objects as possible. Ranging from humans to tanks and cars to mobile phones, the goal is to provide reference material for 3D modelers, scale modelers, replica builders etc.'
The site doesn't include architectural blueprints, it does have a wide range of other objects in some interesting categories:
- WW1 Airplanes
- WW2 Airplanes
- Modern Airplanes
- Science Fiction
Most of the images are vector drawings with some entries that are photo references. The Phones category is almost all photo references, which may be a better choice than vector graphics for those items. Many of the entries would benefit by being a bit more descriptive - for example, five drawings in the anatomy category are all listed as "Back Muscles".
The resolution of the images is restricted to a maximum of 500px wide and 500px high unless you decide to register (free) at the site.
I found that for many things, such as anatomy and handguns, the smaller images were fine. Ships, trains and planes were small and hard to read.
You'll need to supply a nickname, password and email to register.
Registration and membership are free of any costs and allow you to view all blueprints at full size, along with other benefits.
Premium Membership is a one time $7.50 (USD) fee for a lifetime membership.
There are tutorials on using several programs to create blueprints such as Maya, Blender and Google SketchUp should you wish to create your own blueprints.