If it's an AKC registered breed:
http://www.akc.org/breeds/breeds_a.cfm
This will give you pictures, breed standard, and even history of the breed.
If it's a UKC registered breed:
http://www.ukcdogs.com/RegUKCBreeds.htm
This will give you breed standards, some with pictures, and brief history of the breed (very brief but it's better than nothing).
Of course, that only helps if you're in the US. But I think dogbreedinfo is a US site as well, so breeds from other countries may not be on there either. *Note - UKC has a lot more recognized breeds than AKC, so if it's obscure, check there!*