I've been to Honolulu. I loved Honolulu since I really love surfing and the waves at north shore were awesome at the time. It will probably take you a whole day to take in everything on the main strip at waikiki beach. I stayed at the Marriott and I would recommend them. International market has a lot of bargain souvenirs that you can pick up and bargain the price on. You can also check out Aloha Pier.
I used this site to book a dinner on a boat that takes you out on the ocean to watch the sunset (if you have a significant other, you should definitely do this).
http://www.hawaiiactivities.com/
Pearl Harbour was pretty cool too. My recommendation is to definitely rent a car since you'll need one to explore the islands.