What kind of exposure will it have? Will it be tucked in a covered corner basically away from all but the worst elements, or hanging out in the open where it will be hit with rain? I had one that was tucked in the corner of a covered deck, and all I bought was a cheap LCD TV from Walmart, and hung it on a simple mount. When winter came along, I just unhooked the thing, and brought it inside. My new house doesn't have a covered deck so I need a weatherized panel. Sunbright is the best known brand. Their panels start around a grand and go up quickly, I think LG makes one but I haven't seen them in a long time. Runco offers probably the best outdoor TV for picture and weather protection, although be ready for some sticker shock (I think they start around 6k) but they are very tough.
Some others things you will need, is a wall plug, and cable TV connection. I had an electrician install the cable socket with a spring cover so it wouldn't corrode during the winter.