Look what I just bought:
Velvet leggings! I'm so excited! I ordered them earlier this week after some debate, i.e. three emails to friends in which two of them said "no way". I got them today and they're gorgeous! I was a little skeptical because they reminded me of my old jazz and tap dance days (in middle school mind you) but thought that they'd be thick enough that I wouldn't have to wear two pairs since leggings seem to always be so sheer. My friend T said they could never be hot again, but I beg to differ after seeing Diane Kruger's outfit and reading about the new trend on WhoWhatWear.
Velvet is great for fall because it has a nice feel and keeps you warm, plus it's such a rich fabric. I don't know if I could pull off wearing a full velvet outfit, but it's easy to follow the trend with just one piece of your wardrobe. Think pencil skirt, scarf, or flats. If you're interested, you can find the leggings here.