I've had the factoring calculator for a while, but I've just added a rational expressions enhancment to it.
Factor Calculator and Rational Root Calculator
For shortcut commands, simply type the word factor in front of your expressions. For rational expressions, you are allowed one fraction, and you don't need to block off numerator and denominator with parentheses.
Essentially, the calculator will walk you through the steps to factor top and bottom, and then check to see if there are common cancellation term(s). If so, it will show you the crossout line for any cancelled terms, and then the simplified expression.
This is version 1 of the rational expressions portion. Let me know if you would like enhancements or changes. Any other changes sent to me, I'll make on the fly.