I have some extra pasta, cooked.  I have no extra sauce to put the pasta in.  What's the best way to preserve it so it lasts for a day or hopefully two without getting dry or rotten? 
Toss in oil and do not salt. This should help keep the pasta from drying out. Refrigerate until you are ready to use it. Before use, quickly reheat the pasta in boiling water or in a hot pan, which will give the starch a fresher, "just cooked" texture (this is the same reason that you toast old bread) 