I remember two games that I think were on the cartoon network site. One was Samurai Jack and the other was Scooby Doo.
On the samurai jack one, I think it was a basic platform game. As you progressed, you could get better weapons. I think there was a cheat system too, and I remember "Honor", "Compassion", and "Courage" were some of the cheat codes. Gah I want to know what it was.
In the Scooby Doo one, it was a topdown game where you roamed around searching for keys and other items. I don't remember the plot or what you had to ultimately do, but just remember several different environments like a beach, an old yard with fences of some sort, and a house.