One widely used tool for assessing college students is the knowledge survey. The knowledge survey is not a test per se. Instead, at the beginning of the semester the students in the class are given a series of questions and asked, using standard fill in bubbles, to rank their confidence in their ability to correctly answer each question. Then, at the end of the semester they are again given the survey and asked to rank their confidence. The results from these two surveys are then compared.
Portfolios are becoming a very popular way to do student assessments. Portfolios are collected during the semester, and include text, journals, research, and artifacts such as photos, photocopies, slides and other multimedia content. This collection is then judged based on its quality, depth and applicability.
There are a number of online tools, such as SALG -- Student Assessment of Their Learning Gains -- that allow the instructor to place tests, quizzes or surveys online for the students either to take online, or to print, fill out and hand in to the instructor. One of the advantages of students' answering the questions online is that some of these sites will analyze the answers and provide the instructor with graphs and charts to help pinpoint the areas that need improvement.
Of course, all the data you get from these various assessments means nothing if you don't use it. You should carefully analyze your data and look for problem areas. Then determine the cause of these problems. It may be that the instructor needs to change some aspect of her presentation, the texts used or the structure of the course.