I know it is nowhere in the same league, but I thought it was worth mentioning that Eigenmath is a very simple mathematics program that is free and I believe it is in current development. It would not allow for typesetting, but the developer may add an ability to export to LaTex if requested...
Another great resource that I have found usefull is mathworld, an online math encyclopedia http://mathworld.wolfram.com/FundamentalLemmaofCalculusofVariations.html. Wikipedia is good as well http://en.wikipedia.org/wiki/Calculus. Both of these links go to an article instead of the home for some...