Stuff about algorithms; explanations, implementations, and pitfalls.
[>] Explaining the Levenberg-Marquart methods for solving equations
This article explains the mathematical foundation for Levenberg-Marquart methods, but has no source code example (not even in Fortran). Good for understanding.
[>] FreeVBCode
This site is a large and well sorted collection of source code. The code pieces range from banal to excellent, and should satisfy all levels of expertise.
[>] MatrixVB
[>] Using Newtonian Approximation to solve equations
If you want to solve polynominal equations, you can use the Newton-Raphson method of approximating the solutions.

This routine takes parameters too.