This page gives a good description of different types of power protection.
http://www.alliedelectronics.com/Power-Data-Protection.htmlTo protect computer/networking equipment we use power conditioning UPS batteries from Oneac. IMHO, they are best.
http://www.chloridepower.com/en/USA/Products/Technologies/UPSs2/For anything that doesn't require uninterrupted power, a UPS battery isn't necessary. For appliances and general purpose protection against surges/sags, a Transient Voltage Surge Suppressors (TVSS) should suffice. These get hooked up between the BEL meter and your breaker box.
We recently had a customer install a few of these and so far so good:
http://www.ditekcorp.com/product-details.asp?ProdKey=5For the ultimate protection, the best thing you can have is an isolation transformer (aka power conditioner) which gets placed inline on 220v or 110v feeds to your equipment. The isolation transformer does what is says, it takes the AC from the outlet, "transforms" it to DC and back to AC - cleaning the power along the way 24x7.