Beersmith is great and works on most systems, and its only $21. Many people also use Promash although I can't personally vouche for that program. If you are looking for something that is free, try Beer Tools or the Recipator (do a searcvh and you will find them) both offer good free programs, although they are limited to what you are able to do. There are others out there but I think that those are the most common and I can certainly say that any of those will work for most if not all of your needs.
Cheers