At the moment, amorphous silicon (a-Si) panels are the most common for residential use, as they're by far the cheapest watt-for-dollar. The technology is changing all the time, and this promises to be cheaper. Last I checked, the cost of 8% efficient a-Si solar panel was approximately $1000/square meter. These panels will convert about 8% of the solar flux reaching them into DC electricity. (Inverter required, batteries optional) Higher efficiency panels exist, but are outrageously expensive and really only practical for satellites and mars rovers.
About 1370W/m2 of the sun's energy reaches the earth. Multiply that by the cosine of your lattitude. Additional energy is absorbed or reflected by the atmosphere. And then factor in the efficiency of your cell. In the very best case scenario (high noon on a clear day in Texas), you might get 540W/m2 or so striking your panel and about 43W out. In areas further north, it's obviously far less.
Now, panels are always touted as 60W or 100W panels, but that's PEAK, and the actual output depends greatly on your geographic area. The average amount of solar energy hitting that panel on a clear day (nights factored in) can be anywhere from 71W/m2 to 240W/m2- which on an 8% panel would provide about 6-20W of power per square meter (time averaged). Net energy output in a the arizona desert might be as high as 175kWh/year for each square meter of panel. (That's about $12 At 7 cents per kWh)
Here's a good cross-section of solar panel prices:
http://froogle.google.com/froogle?q=solar+panel&btnG=Search+Froogle [This message has been edited by SteveFehr (edited 11-08-2006).]
