Crashman had a good link for replacement batteries for APC. They aren't that expensive compared to buying a new UPS.
I buy used UPSs for cheap. I believe UPSs have better protection for my computers,TVs and stereos, if the batteries are bad for my stereos and TVs, no problem, not like I need to save data on a stereo and TV.
Beware of cheap power strips.
Like Folken said, you can't go wrong with APC, Belkin and Cyperpower. You might be able to find an inexpensive UPS at a thrift store or ebay, the batteries might be bad but you can get replacements cheaper then buying an UPS new.
I don't have any Belkin or Cyberpower UPSs but from what I heard they are good. I use APC. Being able to replace the batteries is very important!
I'm not a number, I'm a free man!