A very good book that I have found very useful on this subject is

"Practical DSP Modeling, Techniques, and Programming in C"
 Don Morgan.
 John Wiley & Sons, Inc. 1994.

It's content scopes from the basics of signal theory to implementation of
DSP algorithms on DSP processors. It contains abundant C code including
FFT, windowing, FIR filters, IIR filters, realtime convolution, and more.
It's written on a very friendly language.
I'm not DSP expert or skilled programmer (just "only" musician) but I could
understand almost everything on this great book.

IGNASI ALVAREZ.

Ignasi Alvarez