I'll start off with a couple I have used. Please share your own that you have created and know to be correct!

* [Albers Equal-Area Conic (Florida)]

"Albers Equal-Area Conic (Florida)", 9, 74, 7, -84, 24, 24, 31.5, 400000, 0

Almost all the data and images on the ~free~ website http://www.labins.org for Florida is in this projection.

* [Mississippi Transverse Mercator (MSTM)]

"Mississippi Transverse Mercator (MSTM)", 8, 74, 7, -89.75, 32.5, 0.9998335, 500000, 1300000

Almost all the data and images on the ~free~ website http://www.maris.state.ms.us/ for Mississippi is in this projection.