I've smoked Salvia four times, and had one REALLY intense trip. It seems the plant has a reverse tolerance; the first time I smoked it, I got nothing. Second time, just a little lightheaded, nothing more.
The third time, however, the entire world tilted slightly down left. That was weird.
The fourth time, everything went sideways, and I started falling off the couch, trying to grab pillows to keep me from falling off. Silliness, but I had no idea what was going on. All I knew was that eyes were watching. The eyes of my friends watching some movie.
Next time I do it, I will be alone, or with a very small number of people. And we shall be listening to Porcupine Tree's Voyage 34.
pretty much every ghetto headshop seems to carry it nowadays too, not that you should buy it from them anyway, unless you can have someone vouch for the quality.