Comment Cyclotrons, He, Muon detectors (Score 1) 249
Superfluid He is also wickedly cool. If you can build something to house it, and pump on it until it gets cold enough, you should be able to do some cool experiments with it.
Though not as visually appealing as a cloud chamber, building a detector to measure the lifetime of a muon was one of my favorite undergrad experiments. Three scientilators stacked on top of each other wired into a bunch of electronics, along with the right formulas, and you can get a reasonable measurement. My prof gave us a Phys Rev paper describing how it was done years ago, access to the parts we needed, a scope, and a computer that had a labview application set up for counting experiments. We figured out the electronic logic from the paper, used the scope to debug and set all the triggers correctly, then had to figure out how to actually calcuate the lifetime from what we measured (along with systematic + statistical errrors). Hard, yes, but man we learned a good deal about real nuts and bolts experimental physics that quarter.