Some otherwise operational amateur radio satellites have store and forward, however none of them appear to have store and forward enabled or working at this time:
AO-7, launched in 1974, included a store and forward message unit, Codestore, cablae of storing and repeatedly retransmitting 18-word Morse code messages loaded by ground stations. It's the same design as was flown on OSCAR 6. The unit is not currently in use, and it's unclear if it's still operational, though many other parts of AO-7 are still functioning.
FO-29, launched in 1996, included a digital BBS that is not longer operational.
You can find a list of operating Amateur Radio satellites on Wikipedia, and searching their names will bring up sites that show their capability. There is also a list of Amateur Radio satellites, including cubesats, and on the SatBlog which may prove useful.
Also note that another launch of many cubesats is occurring at the end of November, 2013, and some of these satellites may have store and forward. Keep in mind that cubesats are very often short-lived without altitude or attitude control, so you will want to focus on the OSCAR satellites that are still operational.