Try searching CiteSeerX:

http://citeseerx.ist.psu.edu/

A google search of the site is sometimes more productive. For instance:

http://www.google.com/#hl=en&q=site%3Ahttp%3A%2F%2Fcites...

or http://scholar.google.com and make use of "All x versions" there's usually a pdf version among them.

I find this is really the best way. It also finds papers authors post on their websites which has been becoming extremely common (kind of like self-publishing)

Personally, I much prefer searching citeseer, as most of the papers I've found through google scholar are behind paywalls, while virtually every paper on citeseer is free.

If I can't find a paper through citesser, I usually just do a regular google search, and often find the paper elsewhere on the web. Google scholar is pretty much my last resort, and I really haven't had much luck finding freely downloadable papers through it.