Similar to what Mike posted above. Red oak boards (4 1/2" x 3/4") with a 1/4" roundover on top. Top of boards is 3/4" above table top to catch any stray tools, scenery, rolling stock or motive power. I think the finished oak gives the layout a more furniture-ish (made up word of the day) look. Skirting is something my mom did as a Christmas gift.
I also like what Dave, Mike and Gilley have done.
Tom