Hi,

Here there are some examples in Verilog of functions DSP for FPGAs,
some of these are:

http://www.altera.com/support/examples/verilog/verilog.html

 * Achieving Unity Gain in IFFT+FFT Pair Using Block Floating Point
Arithmetic
 * Fast Fourier Transform (FFT) With 32K-Point Transform Length
 * Coefficient Reload Finite Impulse Response (FIR) Filter
 * Discrete Cosine Transform (DCT)
 * Basic FIR Filter
 * Time Domain Multiplexed FIR Filter
 * Polyphase Decimation FIR Filter
 * Polyphase Interpolation FIR Filter
 * Two-Dimensional FIR Filter
 * Basic Infinite Impulse Response (IIR) Filter
 * Butterworth IIR Filter
 * Magnitude Function