Is there a way to transmit data and not have the object be unusable anymore?
Since version 0.23, the Mystery Goo Containment Unit and the SC-9001 Science Jr. can not be reused after you transmit their science data, unless you have a Mobile Processing Lab on the vessel (or dock with one which has). The MPL can "clean out" these experiments so they can be used again (It can also "process" any science data so you receive more science through transmitting them). You find these option when you right-click the MPL. Note that both of them require a lot of electricity, so your space laboratory should be equipped generously with batteries and solar panels.
Update: In current versions (since 1.0?) astronauts of the Scientist class can also reset these experiments while on EVA. To do so move the Astronaut very close to the part, right-click on it and pick the appropriate option.