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.
I think there are some useful distinctions one could draw here. Say:
Rationalism is the behavior; rationality is the effect.
Rationalism is the means; rationality is the end.
Rationalism is the community, the movement, the project; rationality is its object.
Rationalism is the body of teachings; rationality is the art it teaches.
I don't think there's a significant risk that historical rationalism (which isn't a particularly contentful doctrine in the first place) will get confused with what we're talking about. Maybe the -ism is harmful. Though there are innumerable cases where the utility of an -ism outweighs the cost. This might be a good place to fight the connotation.