TrailBehind licenses my map layers, so for the major ones (topo, USFS and aerial) you can print maps that match the layers in OTM by going to http://caltopo.com/
and clicking the print icon in the top right. Google Chrome works best as Firefox and IE don't respect borderless HTML printing.
I'm also working on a feature that allows you to draw a rectangle on the screen and create a PDF of that exact area, which bypasses a lot of the browser printing quirks and lets you do thinks like exact 1:24k scale maps, for people who are into that sort of thing. It's all done, I just need to upgrade my server first because PDF generation eats up a lot of memory. This will eventually be a paid feature but the in-browser printing will remain free.