What we now refer to as "Independence Hall" was originally the Pennsylvania State House. This building held important political meetings including the signing of the Declaration of Independence and the creation of the Consitution. Tours are offered and they are free. I certainly recommend everyone check it out even though it is a bit of a tourist trap. The Liberty Bell, however, is another story. In reality, it is not all that significant. It was the bell in the Pennsylvania State House when the Declaration was written. It was forgotten until an abolitionist wrote a poem mentioning this bell. All of a sudden it became a big tourist trap. Well truth be known, the bell is rather small and as told, the story is quite dull.
Unique Suggestions: You can receive a time for the Independence Hall tour. You have to wait on line for the Liberty Bell so get there early.
While it is the "birthplace of our country", it is just so overrated. Crowds and homlessness everywhere, you can't even really go into or do anything at any of the buldings. Way too touristie, just go at your own risk.
Unique Suggestions: Try the underground museum, where you can pick up telephones and call famous people of our country from the past.
Fun Alternatives: The surrounding area, a./k./a. Center City, has a lot of stuff to do. Just walk around, plan trips to places, etc.