Recently, the Fibonacci Calculator was released. This PHP script can calculate the n^th Fibonacci number at high speed, for all n below 50,000. This script, in fact, does not use a recursive formula, or even an implementation of Binet's. I've found that scripts based on those two tend to run much more slowly as n grew, whereas a certain loop (the source can be found here) ran far faster. However, this calculator, along with the Primality Tester, are only the beginning. I am currently working on an advanced PHP expression evaluator. It will be able to handle expressions like:

2^10000
10000!
2^(phi+pi^(e-log(2*sin((5*pi)/7))))
sqrt(f(10)^77)
(phi^101)/(phi^202 - (-1)^101)
phi^(z(pi))
273^273
sin(cos(tan(sec(csc(cot(x))))))

In addition, it will have a huge array on functions: some to test for primality, for the prime factorization of the number, for the geometric/arithmetic/harmonic/root means, and much more. The code, once the evaluator is finished, will be available for download by anyone interested in seeing the source.

The evaluator should be a highly fast program capable of easily handling numbers around 10^30,000, and with varying success after that.