Rationalism should not be confused with rationality, nor with rationalization.
-Wikipedia article on rationalism
I frequently see people using rationalism in place of rationality. Usually other commenters understand them, however I believe that using the word rationality is superior. The Less Wrong tag line is "A community blog devoted to refining the art of human rationality". On the other hand, rationalism is the philosophical term for a very different epistemological position. Furthermore, -the -ism suffix has some undesirable connotations.
There was a post 2.65 years ago making the same point: Note on Terminology: "Rationality", not "Rationalism".
Back then, the confusion between these terms seemed more salient, but Google results count doesn't support this impression (4.8% of "rationalism" in 2011 vs. 4.2% of "rationalism" in 2013). The result count from Jan 2011:
Current results (Sep 2013):