One of the things that makes Sketchup such a fast modeling tool is the 3D Warehouse. The 3D Warehouse is an online repository where anyone can upload and share their 3D models with anyone in the world. This makes Sketchup an even faster modeler, because sometimes it's just quicker to download a model then make it yourself!
Right now the 3D Warehouse is like the wild wild west. Anyone can post content to the 3D warehouse. From large companies to Hot Pocket fueled basement dwelling teenagers. This makes what you can find in the 3D warehouse a bit of a mixed bag. Here is some photographic evidence of the problem. (Note that my kitchen IS drawn to scale here)
This was the top hit for the search "Plate"
This was the top hit for the search "knife"
This was the top hit for the search "coffee maker"
As you can see, a LOT of these models aren't drawn to scale. That doesn't mean they aren't usuable though! A simple use of the scale tool will solve that.
Now, what you have seen so far are amateur efforts at creating models. Honestly, there are some great amateur attempts out there. The biggest mistake made is not drawing things to scale. Using the scale tool fixes this really quickly. If you can get over that, there is a lot of great stuff out there.
But what about real products, ones that are guaranteed to work, and are models of actual things that you might specify? Well a lot of companies have stepped up and created some wonderful models that I use on a daily basis.
Here are some links to some notables (in no particular order)
These are great models. Contained in each model is a wealth of information. See this post to learn more.
This is a great collection of cabinets. What's nice is not only do they make the individual cabinet models, they also make available displays and other designers projects for download. It may look a little overwhelming when you first see this collection, but it's full of great models that you can download and explore. Use them for inspiration on your next project!
I don't sell appliances, so unless I am trying to find the exact model a customer has, I use these. Why do I use these? This is the biggest collection of models of appliances on the 3D warehouse. They all match each other, and they are organized very well. Jenn Air is trying to get designer "Mind Share" by making these models really easy to use, and its worked!
I maintain a list of products that I think are great models. These are ones that I use frequently. Click here to see all of my collections.
If you are signed into Google when you go to these, you can add my collections to your collections. What's nice about this is that when I update my collections yours will be updated too. Not only do you not have to model, but you can let me maintain your collections as well!
Happy Sketching!