Drew Kerkhoff's introduction to R
R-Studio - this is where you can download a copy of R Studio and R
R Project For Statistical Computing
Graph Pad Quick Calcs - From GraphPad; basic stats, distributions, tests of all kinds - first place to check
Binomial Probability Calculator - from Vassar; binomial tests, binomial distributions, etc.
Chi-square Calculator - from Texas A&M; visual representation and numerical output for Chi-square distribution
Handbook of Biological Statistics - online textbook from the U. of Delaware