Sorry for the short notice, but I wasn't expecting a Test Day on a Sunday! Today is SSD caching Test Day. This is a shiny new feature in Fedora 20 which supports using an SSD as a cache for a larger regular hard disk, using a kernel feature called bcache. As this is a brand new feature in Fedora 20 it needs testing, so please, if you can spare an SSD and a regular disk temporarily for testing, come along and help out!
As usual, the Wiki page has testing instructions, test cases, and a table into which you report your results, so head there and follow the guide! Also as usual, the Test Day organizers will be hanging out in #fedora-test-day on Freenode IRC to discuss bugs and help out with testing, so please join in there too. If you don't know how to use IRC, read these instructions, or just use WebIRC. Thanks!