There are two basic tools that folks use here on Flyertalk, ExpertFlyer and KVS, and each have their various strengths and weaknesses. KVS pulls all its data from publicly available websites, though I do find it MUCH more convenient to have it all on a single screen (and storing PNR information rather than logging into the various websites). Great time saver.

Both expert flyer and KVS tool are maintained by Flyertalkers, and both (at least in the most useful versions) come at a price. KVS Platinum is $30 for 6 months IIRC.