This morning I pulled my homebrew two-elelement triband yagi up. I got the design from a QST article:
http://www.arrl.org/tis/info/pdf/0111035.pdf (ARRL members only)
I need to pull it up a little higher, but when I'm done, it'll be in a sloping configuration, with the feedpoint at about 35 feet. Just listening around 20m now, it's a really significant improvement to the east coast - a W2 calling CQ was down in the noise on my G5RV, but was much better copy on the beam.
If the antenna performs as expected, this should give me about one S-unit improvement at a heading of about 70 degrees.