While searching for a rental in oahu I came across this site with some really great oahu vacation rentals. Great site with some cool rentals and the prices seemed reasonable.
I recommend renting a condo or a house during your stay there..u can find alot of good listings on craigslist-hawaii. Or if u are active or retired military only try the Hale Koa..last but not least if u wanna really rough it and do not mind living in co-ed dorms kinda style try the Hostels, for like 25$ a night u can share a 8bunk room or for 45$ u can have a private 2 bed room, but the 2 rooms ajoin..and most of the hostels are a couple blocks fom waikiki.. good luck have fun
One good place to save money is by getting a monthly rental. You find these on bulletin boards in many hotels. Not always easy to find. For example, The Island Colony has quite a few owners that rent for around $1,200 a month. My friend and her goirl friend rented one studio together so it came to $20.0-0 a day. Even if you stay for less than the whole month you save over a daily rate. I have numbers from that bulleting board, but don't think I should list them publicly. Write me if possible and I can send this info.
BeachListings.com is also looking to expand into this area and list some rentals. It's a beach rental site that offers three times the pictures for the same price, and is currently giving a buy one year, get a second free.
The best luck we had was VRBO.com (vacation rental by owner). They have all privately owned places which are usually cheaper than the hotels. Mostly condos at all locations. Our favorite site for vacation rentals.