[cdavid]

The website by Julius O Smith noted above is a goldmine for a lot of theoretically grounded but practical descriptions of many algorithms. Then, you have http://www.musicdsp.org which has a lot of code snippets, + the ML is frequented by some of the most gifted programmers in the area of music softwares.

I have noticed that papers by Jon Dattorro are now online: Jon Dattorro is the guy behind a lot of ensoniq and lexicon stuff, and he knows a lot about both practical and theoretical aspects (look for "Jon Dattorro aes" for his seris in the journal of AES).