The difference in sizing between regular and petite dresses is the length. Petite clothes are made for shorter women so the length at the bottom of the dress and on the sleeves would be shorter.
The only major difference between petite formal dresses and regular formal dresses is that petite formal dresses are made to cater to women who are short in stature. So, certain elements of the dress, such as the skirt/train or the straps, may be constructed shorter in order to accommodate the smaller frame of a petite woman. Besides that, petite formal dresses are often identical to regular formal dresses in terms of styling, cut and adornments. When picking a petite formal dress, it is best to choose a dress that works to lengthen your torso. Gowns that are one color are good choices, as are gowns that don't have too many layers. Petite women are advised to avoid dresses that have large or horizontal patterns, drop-waist syles, dresses with too many gathers and dresses with belts.
Regular and petite in jean sizes refers to the rise in the jeans. While the leg length of regular jeans is longer than that of petite jeans, the main sizing difference is in the length from the crotch to the waist.
Donnaricco.com is a great place to find dresses for any season, they have new summer and fall dresses daily. They do have petite sizes as well as regular sizes, and you can even search dresses by occasion as well!
PETITE IS FOR SHORTER WOMEN
I would recommend DressPro. They have a great selection of affordable dresses in many petite sizes. http://www.dressespro.com/petite-dresses-c-1_100.html
petite sizes are for short women that would need to hem regular sizes because it fits too long
Petite formal dresses are gowns for a formal event like a prom or wedding, that are made to fit women of a petite stature. Petite sizes are women's 0-3.
The plus sizes are for full figured women.
A lot of stores in California carry petite formal dresses. Major retailers like JC Penney and Macy's have entire petite sections.
David's Bridal is an excellent selection for bridesmaids dresses. They have several options for sizes including plus size and petite. Empire style dresses work good for both plus size and petite.
David's Bridal
Below is the link to one of the sites with prom dresses in size petite.