Musical Improvisation in the Baroque Age
http://www.wright.edu/~martin.maner/improv01.html
This site is a good resource for learning about basic harmonic and melodic strategies applied in Baroque composition. With score, text, and audio examples, the site demonstrates the technical rigor required by musicians of the time for the realization of basso continuo.

Late Renaissance and Early Baroque Stylistic Comparisons
http://plato.acadiau.ca/courses/musi/callon/2273/ren-bar.htm
An easy to read chart comparing styles and approaches of these two periods is presented here, with emphasis on sacred music.