Well, because petunias require so much deadheading, I don't usually grow them. However, last year, I did grow the Pirouette Petunias and they were just beautiful (especially the purples)! I bought the seed from Parks Seed at http://www.parkseed.com/gardening/PD/1583/

I love Petunia 'Laura Bush'. The flowers are smaller than other hybrids, but it is vigorous, does not peter out fast like others and fragrant to boot:

I planted very small seedlings the last week of May. Here they are on June 16, 2 1/2 weeks after transplanting:
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July 4:
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July 14:
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I sow my seeds in February or March the Winter Sowing method, i.e. sow them in a container, cover with a clear piece of plastic with drainage and ventilation, leave them outdoors in the sun and snow. They germinated in early April.

I have had very good luck with a type called 'Prism Sunshine'. They grow very easy from seed and don't really require a lot of dead heading unless it is a VERY wet year, then they tend to get yucky (as most petunias do in wet weather). I will put up a link so you can view them. I also really like the Blue Wave Petunias (which are really dark purple) but I have never grown them from seed.

Here is a link that might be useful: Prism Sunshine Petunia from park seed