Upgrading from:

Algebra`PolynomialPowerMod`

The functionality of PolynomialPowerMod is now available in the kernel function PolynomialRemainder.
Modulus is now an option to the kernel functions PolynomialQuotient and PolynomialRemainder.

Compute a power of a polynomial modulo a prime and a polynomial:

Version 5.2 << Algebra`PolynomialPowerMod`
PolynomialPowerMod[x^2 + x + 1, 400, {x^3 + x^2 + 1, Prime[4750]}]

The original package is now available on the web at library.wolfram.com/infocenter/MathSource/6758.