My Hackaday Prize entry needs a solar charged battery back to power the sensor and transmitter I'm placing in front of my house. Rather than spending a whole lot of time finding domestic suppliers of small photovoltaic panels and trying to spec a nicad or nimh battery pack, I decided to buy a "60 LED Solar Security Light" from Harbor Freight just a few miles from here. The list price was $32.99US, but it was on sale, plus I had a 20% off coupon so it ended up costing me about $20.00US. I doubt that once you consider shipping, I could have bought a solar panel and battery back for less than that. What's more, I ended up with a big LED panel and a motion detector module for use in future projects.
Here is the video of my teardown and analysis of the light:
Here's a link to the Security Light on Harbor Freight. NOTE: Products at Harbor Freight change very frequently, so by the time you are reading this the link may well be bad. If that happens just search the Harbor Freight site for "Solar Light" and you'll probably find very simular products.
Link to my light: 60 LED Solar Security Light
Link to HF home page: http://www.harborfreight.com/