Ask ten knitters what their definitions of beginner, intermediate, and advanced are, and you'll get ten answers!
The thing is, a lot of the "hard" parts of knitting (e.g. cables, knitting in the round) are NOT that hard! I've never heard of anyone who couldn't figure out cabling. And knitting in the round is just like knitting with straights, but you just have some needles holding stitches in the back.
For an intermediate class, I would suggest socks, mittens, cables, simple lace, and maybe some Fair Isle colorwork. I would consider intricate lace, intarsia, and entrelac more advanced.
Did you see the entrelac primer in the newest (Spring 07) Interweave Knits? It's very well-written and easy to use.