There are some Framework classes out there that are useful, but infrequently used. In my experience, System.Web.UI.Pair and System.Web.UI.Triplet are two such examples. These provide basic utilities (like serialization) to store two or three related objects into single object. They have predictable members, for example Pair has a "First" and "Second" property that can be set either in the constructor or once instantiated.
They're simple classes, but are easy and helpful to use in web applications. Of course you could write your own container, but this saves you the step.