Well, the answer above was informative although a bit extreme. There are many kinds of chemotherapy, and the side effects depend both on the type and the dose of chemotherapy. They may include hair loss, ulcers of the mouth, nausea (which has quite effective treatment), diarrhea and the most problematic: damage to the blood-cells producing tissue in the bone marrow that may lead to infection.
Other side effects may occur only months or years later, but are usually type-specific.
It's a vast subject, so you may ask about specific drug or read more here:
http://www.nlm.nih.gov/medlineplus/cancerchemotherap...