Another great resource is Ted Cohen's recent book, Jokes: Philosophical Thoughts on Joking Matters . He explores how jokes work -- what makes them funny, what makes them offensive (when they are) -- as well as what jokes can do beyond simply making us laugh. Full of good examples.

I completely agree with the reasons Sean Greenberg gives for thinking that the history of philosophy is philosophically valuable, but I'm inclined to think that knowledge of philosophy's history is important for doing contemporary work, for exactly the reasons he offers. Knowledge of the history of philosophy helps contemporary philosophers to avoid re-inventing the wheel, with respect to both the questions we ask and the solutions we propose. More generally, I would add that, while false claims can't 'ground' anything, they can be extremely valuable as pointers towards more promising directions. The possibility of learning from one's mistakes shouldn't be underestimated!