There are many types of master's degrees, including Master of Arts (MA), Master of Science (MS), Master of Business Administration (MBA), Master of Fine Arts (MFA), Master of Arts in Teaching (MAT) and Master in Pharmacy Studies (MPharm). There is a type of master's degree for nearly every field of interest--from Human Relations to Research to Geography. Chances are you can find the right program for your interests, which is a good motivator for continuing your education.
In many fields, having a post-graduate degree will put you ahead of the pack. If you want to rise to management level in business, an MBA is often required. A master's degree can give you an edge over other job applicants when moving between companies as well.
Obtaining a master's degree places you in a higher salary bracket. Typically, the starting salary for a person with a master's degree is at least $10 thousand more than for a person with an undergraduate degree. While job experience will eventually lead to the higher salary bracket, a master's degree gives you a jump start into the higher wage level.
Chances are that tuition reimbursement is part of your company's benefits package. The cost of tuition can be lessened, or absorbed completely, by your employer if the degree is job related.
If you are at a point in your current career where you think that you cannot get any further ahead, or you have lost interest in your field, pursuing a master's degree in a new area can redirect your career path and goals. A graduate degree program will expose you to a new field and send you out to a level playing field when the time comes to find a job in your chosen area.