Best online calculators Here are a few websites that have online calculators: www.quickmath.com - powered by webMathematica: this site is very handy and will do algebra (factoring, simplify, partial fraction decomposition, expand), solve equations/inequalities (single or a system), plot equations/inequalities (single or a system), derivatives, definite or indefinite integrals, and do matrix arithmetic/inverses/determinants. Suggestion: for those who post "Will someone please check this [problem/integral/derivative/calculation]..." or the like, cut and paste the above paragraph as a reply. www.integrals.com - powered by the Mathematica engine: just what it seems, but it will only do indefinite integrals. www.livephysics.com - has these tools: Evaluate Function, Function Grapher, 3D Function Grapher. Very nice since the 3D Function Grapher allows for you to plot a 3D function and then cut and paste customized UBB code from the page into a forum post to embed the plot graphic you made into your post (see add). http://people.hofstra.edu/faculty/Stefan_Waner/RealWorld/utilsindex.html [Broken] - includes these categories of utilities/tools: Graphers, Regression Tools, Matrix and Linear Algebra Tools, Probability and Statistics Tools, Calculus Tools, Math of Finance Tools, and Miscellaneous.