When you say "long term", do you mean 10 years or ten months? People tend to see "long term" as different lengths of time.....
If you are thinking along the lines of 10 years or more, the stock market is the place to be, especially when there are some great, blue chip stocks selling cheaply right now. A Vangard index fund based on the S&P 500 is a no-load fund with a low expense ratio, an excellent way to park some money for the future.
If you have a shorter time frame in mind, say 5 or fewer years, a bank CD could be the way to go. With interest rates as low as they are right now, there really isn't much thats traditionally safe paying much in the way of a decent interest rate.
Also, if you have any debt at all-- car note, credit card bills, get rid of them first before anything else. That alone will save you some $$$. I'd even consider paying down your mortgage with the money as well. If you have a 6% interest rate on it, any extra money applied towards the principal saves you lots of $$$ in the long run......