With the raspi I believe you've only got one 100mpbs ethernet port, so you'd probably want to buy a usb ethernet adapter.
This is actually a question that we've been grappling with for a while. With the rise of this broad array of embedded devices, we're really curious about affordable mini-computers that could be attached to the mesh for a variety of purposes. It would be terrific to connect a raspberry pi-like device to the mesh and serve an own-cloud instance, or an etherpad, or provide VPN services, or some sort of bulletin board, or provide a locally cached version of wikipedia, or .....?. We've pre-ordered a couple of the new tessel 2.0 boards (because we happen to enjoy javascript and because they're a local company so we've gotta root for them). For more performance routing and the like, the PCEngines are probably the next best option (and we might consider them in locations where we'd like to actually do encrypted tunneling for
peoplesopen.net connections). I have access to a couple soekris net650 routers, but the price point on those makes it pretty out of our league for most purposes I think.