I use CiteULike (http://citeulike.org) to manage papers a lot.
Unfortunately, I don't have access to paid site. But some authors
are generous enough to put pdf on his own site, which I find
using google search.

javascript:(function(){
var title = document.title.substring(11);
var query = '%22' + title + '%22 ' + 'filetype:pdf';
var url = 'http://www.google.com/search?q=' + encodeURI(query);
window.open(url);
})();

It simply takes the paper title from windows title. Then it searches the title(enclosed in quotation) for pdf files of the same name.