Ok, first, let's get one thing clear: SNOT, in this case, is not referring to that nasty mucus that unfortunately seems to always seep out of your nose when you're on a date. No, SNOT stands for Studs Not On Top, a building technique that spans LEGO themes and genres, from Castle to Space to Trains to Town to Pirates to Technic to everything in between. SNOT is everywhere, and SNOT is extremely useful. Now, there are way too many SNOT building techniques out there to feature in one blog post (and new ones are invented every day), but this old thread at the Classic-Space forums highlights several very common techniques, such as using two highlight bricks and a plate to create this nifty configuration:
Look for more SNOT constructions soon!