I am compiling a list of ideas, notes, and links for people working with PICs and Si570 devices. I have some future projects that I am researching for when I have some homebrew time.

PicAxe + Si570 (some interesting notes on freeze & unfreeze)
http://www.dspradio.org/df7tv/src11

Si570 vfo with 16f628 and Si570
http://g4oep.110mb.com/si570vfo/570VFO.htm