I'm curious as to what sort of problems show up on an ultrasound?

Ultrasound: It depends on the type of ultrasound. Ultrasound is very accurate in depicting many types of abnormalities. Since there is no ionizing radiation involved, and it is relatively quick and inexpensive, it is often the first imaging study performed.

You can: Ultrasound most of your body so too many to list

Depends: It depends on what part of the body is being scanned. If it is the thyroid it can detect cysts or tumors, same thing with the breast or liver. It is often used to look for gallstones, liver disease, kidney stone/cysts, ovarian cysts/tumors etc. etc. It can be used to look at blood flow through veins or arteries, and the most common scan - evaluating pregnancy. Hope this helps.