The 'check engine' light means that a trouble code has been detected. If you do not have access to an OBDII code reader, some parts stores will scan the codes for free. Read the codes, and post them in this thread.
OBD-II Trouble Code: P0171 System Too Lean (Bank 1)
Do the symptoms presented with this code sound familiar?:
You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.