I'm in the process of learning XSI (Foundation), having come from Lightwave (well, still using it actually). One major difference between LW and XSI is the surfacing workflow moving from LWs relatively simple (and dare I say intuitive interface) to XSIs node-based interface.
I was thinking it would be a good idea to download some shader presets from some of the sites you guys have mentioned and deconstruct them (as well as run through the many tutes), but here's the real XSI newbie question, once I've downloaded them where on earth should I put them within the XSI install folders?
OK, well feeling suitably "first day at schoolish" and hoping no-one steals my dinner money, I'm going to stand in the corner of the playground and hope someone makes friends with me :o)
ps - this app has some amazing features that would be awesome in LW *sigh*