I was looking for something with a bit more "bulk" to it than a skinny t-post. Galvanized u-channel posts were never an option, we we talking about 6" diameter round posts. You find those for $36 I'll come get them.
I ended up stumbling across the perfect solution at Home Depot. They've discontinued their 4.75" x 4.75" x 100" PVC post sleeves. Normally they're about $40, I picked up 10 of them for $10 each. I kind of went with what Dan said, I cut the PVC posts in half, slid them over the posts, then "capped" the gap between the 4.75" square PVC and the 3.5" wooden post with 2" wide wood strips, caulked it all and painted the whole thing satin black. The thick post with the thinner post coming out ended up with a damn nice "architectural" look to them. I had less than $20 in each one and maybe 4 hours of install/construction time. I'll get pictures next week when I go back down to install the sponsor signs.