At college you have a very different relationship with your teachers than in grade school. This will allow you to consider gifts such as alcohol, which would traditionally be a gift to a friend or colleague. A bottle of wine will be much appreciated by your teacher, and you can choose a bottle of wine related to your budget. As a rule, a bottle of red is a better gift than a white, unless your teacher has expressed a particular preference.
College teachers and professors usually have offices which are filled with academic and intellectual items. Old maps fit within this scheme, and are an interesting and unique gift. If you are buying an old map, it is best to club together as a group to buy it, since they can be expensive, although this gift will be one which your teacher can treasure. Buy one related to her area of expertise or area of origin.
A box of chocolates is a simple and inexpensive gift idea which you can get for your professor or teacher. This gift is suitable if you do not have a particularly close relationship, or a knowledge of their particular tastes. A box of chocolates is a good gift for a professor who wrote you a reference or letter of recommendation, and you wish to get a small token of your appreciation. A box of chocolates is a gift which is not ostentatious, but often much appreciated.
Often, college teachers receive a wide range of gifts at the end of the year. However, taking the time to write a thank you letter or card expressing how grateful you are for all his help is something which will be more meaningful to the professor. Perhaps when you get a job you can write a letter to say thank you, and provide an address to stay in contact. Your teacher will be extremely touched, particularly if you stay in contact in the long term.