This amendment makes it clear that the federal government only has exclusive powers over what is explicitly delegated to it within the constitution, and everything that falls outside of the constitution can be retained by states. This does not mean that the federal government has no control over states actions, though. There is a reason that the drinking age in every state is 21, and every states speed limits are relatively the same. Congress can withhold funding from a certain state if it makes certain changes that the government does not want, or does not want spilling over to other states.
This video is an interview with a congressman about the tenth amendment. He is talking about the federal government encroaching on states rights under the tenth amendment such as education and health care. He believes that the government should have no say in these issues at all. It is hard to decide whether or not the government making federal standards in education or regulating things like healthcare is constitutional or not, because there is no way the founding fathers could have known about how our educational system or healthcare system operates or is funded. I think a lot of the debate about this amendment stems from whether or not we feel the constitution should be interpreted literally or is somewhat of a living document.
This cartoon is depicting the recent controversy over medical marijuana. This is an example of where the tenth amendment protected the states rights to allow the use of marijuana for medical purposes.
