I've been recommending Raspberry Pi for a while now as a solution for this, but there have been problems reported with the performance of the Pi when printing directly from Octoprint (as opposed to loading to the SD card and using Octoprint to kick off and control the print). What has been suggested is to use something like the Beaglebone, which has the edge on performance. If you're just using Octoprint to load onto SD and print from there you're golden with the pi.

Neither the Pi nor any of its alternatives would be particularly good at slicing, though.