Here is a collection of the in my opinion best cartoon-related Transformers sites I've seen on the Internet. Note that the list is somewhat limited as I'm not a fan of the comic book, fanfiction or Beast Wars.

The Cybertron Chronicle
One of only a few good Norwegian Transformers pages; features include lots of pictures and a supreme voice gallery with icons of all the Transformers plus at least one voice sample for each TF character that had a speaking line on the TV show
A site that has a lot of info about Transformers, a lot of updates, and includes the famous Complete Transformers Listing Page
The Nordic TransFans Association
A Nordic Transformers fan club that I'm a member of
My entirer Prod cel collection at Rubberslug
From series like, He-Man, Transformers, Beast Wars Neo, Blackstar, etc