The APC Back-UPS ES 500 is good hardware. It's a $60 uninterruptible power supply, quick battery backup for when the power dips or dies. Think of it like a better surge protector, good when you're in a neighbourhood with flaky power.
The battery is small. I've plugged in way more than I probably should, so I only get two minutes of battery life. But that's about one minute and fifty-five seconds more than I really need. It's nice to have the "smart" UPS: plug the USB cable into your Windows or Linux box and you get a log of outages, automatic shutdown on power failure, etc For Linux, you need apcupsd to do the work.
APC makes a huge variety of UPS products from these cheapo power strips to megawatt scale datacenter power units. The ES line is nice for home use because of the power strip form factor. If I were buying another one, I'd pay the extra $20 for the beefier battery in the ES 725.