During 2007 this simple solar photovoltaic (PV) system has provided some of my energy needs (OK, a pretty small percentage I'll admit).
In total there are approximately 40W(peak) of PV panels. This charges a sealed 'gel' type lead-acid battery with a charge controller to ensure no overcharging. The battery can then be moved and used to power various devices including 12V lights, laptops (through a suitable converter) and audio equipment (through a pure sine wave DC to AC inverter). There is a display to show the power being fed into the battery along with the battery voltage.
Two batteries are used in rotation, with one being recharged while the other is used.

Four amorphous silicon (cheap, but not very efficient) panels provide around 40Wp to a battery and then (via a DC-DC converter) to my laptop.

The green box contains the charge controller, batteries and system monitor.

Inside the battery box.

The battery box.

The home-built system display - shows Volts, Amps and Power. Based upon a PIC microporcessor.

Home Power magazine Tons of info about on and off-grid PV (and other RE) systems. READ IT!
Alternative Technology Association Australian association which publish ReNew magazine