Animators often do this by setting a keyframe, but you have to use it carefully (e.g. watch the tangents so the key doesn't affect other animation; don't delete it inadvertently etc.).

Here are some alternatives:

Attribute Preset: This can be stored in the Attribute Editor by pressing the Preset button and selecting Save Transform Preset... This will make the preset available for all transform nodes which means that you can build a lot of them up over time. You can blend between different presets to get different poses.

getAttr/setAttr script: There are a number of scripts around that will get the attributes from a node and store them. They can then be retrieved for the same node or another node. There's a nice one in the Bonus Tools called Store Pose that will create a shelf button for easy retrieval. Like Attribute Presets, this can add a bunch of data to your environment - in this case, shelf buttons - but the poses will be available between different files.

Trax Pose: Not everyone like using characters and trax, but for those who do, you can create a Pose. A pose is like a clip but it only stores data for a single frame, instead of a series of frames. A Trax Pose is stored with the scene so you may have less clutter in your environment. The poses can be exported for use among different files.

dagPose: There's a MEL command called dagPose. It's let you store the transformations on a node or series of nodes - it's actually what is used to store the skinning bind pose. Here's a simple example for a selected object:

//save a dagPose
dagPose -save -sl -name myDagPose;

//restore the dagPose
dagPose -restore myDagPose;