I’m actually not that much into the petunia as a flower, but more because I like the word. Still, my site is called Petunias so here are some links:
History (and more pictures)
The petunia is a fairly new garden flower. It wasn’t discovered until the late 1700s and it wasn’t until the 1900s that the modern shape and wide variety of the petunia really came about. You can read more about the history here (this is a nice site with a slideshow, history, and quite a bit about the planting and care of the flower). I think this is the best single site that I link to if you want to see and learn about petunias.
I might add more links and information here, but then again maybe not. Let me know if you find any interesting sites.