Update: First KickSat is now officially in orbit since today, April 18, 2014 and the 104 Sprites will be deployed in 16 days after the launch giving KickSat CubeSat enough time to complete its system checks. The 3U CubeSat unit was deployed onboard the SpaceX Falcon 9 during its Dragon SpX-3 mission:
The 3U CubeSat consists of a 1U avionics bus that provides electrical
power, active attitude control, command and control systems and
communications for telemetry downlink and command uplink. The
remaining 2 CubeSat units are dedicated to the deployment mechanism
that holds and secures the Sprites during launch and in orbit using a
lid. The mechanism can hold up to 200 Sprites and uses a spring-loaded
pusher and by a nichrome burn wire system to deploy all the Sprites.
The prototype mission launching on SpX-3 carries 104 Sprites. The
KickSat CubeSat weighs 5.5 Kilograms.
Source: Spaceflight 101 article on Dragon SpX-3 Cargo Overview
And this is how each of these 104 Sprite ChipSat femtosatellites look like:
And the whole 3U KickSat with the ChipSat trays, release mechanisms and main bus unit looks like this:
All images credit: KickSat on HitHub (includes more info and a video of KickSat sprite deployment). All 104 Spite spacecraft will be deployed at intervals on a timer starting at 4:00 PM EDT (20:00 GMT) on May 4th.
Not yet flying on their own (but already used since 2011 when they were attached to the ISS external platform for testing), so this is answer is a bit premature for this question, but in December 2013 the now successfully crowd-funded KickSat project will launch first free-flying Sprite femtosatellites in low orbit, presumably onboard the SpaceX CRS-3 ISS resupply mission:
KickSat's Sprite femtosatellite design prototype in hand, the size of a couple of postage stamps.
Three prototype "chip satellites" were launched to the ISS on Space
Shuttle Endeavor on its final mission in May 2011. They were attached
to the ISS external platform Materials International Space Station
Experiment (MISSE-8) for testing.
As far as future plans go, a bit confusingly also named KickSat (maybe KickSat 1 rather?) will be a 3U P-POD CubeSat (housing a 1U avionics bus and a 2U Sprite deployer) carrying 128 of Sprite femtosatellites into space, launched as auxiliary payloads through the NASA's ELaNa program, and will be deployed in low Earth orbit (between 300 and 350 kilometers).
Artist's impression of the KickSat deploying Sprite femtosatellites (source: KickSat on GitHub)
After being released from the P-POD, KickSat will perform a de-tumble
maneuver and establish communication with Cornell’s ground station.
After check-out, the spacecraft will be put in a sun-pointing attitude
and spun up to maintain that attitude. A command signal from the
ground station will then trigger the deployment and the Sprites will
be released as free-flying spacecraft.
After deployment, telemetry and sensor measurements from the
individual Sprites will be received through Cornell’s ground station
in Ithaca, NY, as well as several other amateur radio ground stations
throughout the world.
More information on KickSat's Sprite femtosatellites can be found on the KickSat's KickStarter and KickSat's GitHub pages.