I have a small 2nd home that I am trying to light up a little better for security reasons since I am only there on weekends. I want to light up the back area with one of those dusk to dawn lights, but all I can find are those that are motion sensor type lights that need to be plugged in. I am looking for one that is solar powered so it does not require any plugging in, and will be on all the time once it is dark. Can anyone direct me? Thank you.

? Any major hardware store, home depo, Lowe's and more

12 Volts system is what I would do. Solar Panel, Charging circuit, Battery(s),12 Volt Motion,
And 12 Volt Lights. A lot depends on how much lighting you need. More lights mean bigger everything, If not high traffic, you can get away with smaller battery(s)?

The actual light output from one of the solar powered floodlights is not that much. I had a solar floodlight that didn't give off as much light as I had hoped it would.

You might want to check out the new LED lights and see if that fits the bill for you. It costs much less to operate and you can get it to go on at dark. I'm not sure they come in solar powered yet.

I will agree, with the solar, I have had 4 or 5 different ones and never found one I was happy with.

You can do Led's with 12 Volts, They most always see DC volts anyway. Tri color LED's light yellow with AC(Red and Green combined). You can make the system as bright as you want. Batteries and Solar Panel size is key.
The hard ware store type, may not light long enough or bright enough light.
Found this:
NEW Solar Panel Power Motion Detector Security Light - eBay (item 220192799684 end time Jan-23-08 19:15:00 PST)

Go with electric if at all possible. The solar powered will just disappoint you.

Electric is OK. If you are in a remote area, Need backup when power fails, and even a cost savings since you need to invest in a system that works when power fail, Natural Disasters even.
I live in the Florida Keys and Destruction of utilities is a common occurrence after Hurricanes, I am an Electrical Contractor, But Love the Use of 12 volts, Communications, Security, Lighting, Pumps. And be charged By Solar, Wind, or my truck.
A cheap Solar System will dissapoint you. It does take a Little Money to do it right.