I went at the beginning of June, and stayed at the Mirage (which was the perfect location, might I add...literally right out the door are the Forum Shops--MAC Pro!! It was perfect)
Due to location, my must sees were Ceaser's Palace, Bellagio (at night, of course), Treasure Island-the Sirens show outside at night, the Venetian, etc. If I'm not mistaken, the Wynn still gives you $10 to gamble when you get the card from their casino, which is sweet.
I highly recommend getting a bus pass on days/nights you want to hop all over the Strip. The buses are called "Deuces" (cuz they're 2 levels). They're new, nice and hella convenient. Everything looks close together in Vegas, but it's deceiving how far you have to walk at times. Also, the buses take you to downtown as well, which is fun.
Yep, previous comments were right about the VIP passes. During the daytime, you will come across many opportunities for free VIP club passes. Just like the call girl cards, they are literally everywhere, lol. My bf and I used passes at the Beatles LOVE club at the Mirage one night.
A must see for me was the Palms. We took a shuttle over there one afternoon. I had to see all the Playboy stuff, lol. It was a gorgeous hotel though. I would have absolutely loved to go back at night just to go to the club Rain and to go to the Voodoo Lounge, which didn't open til after 7 pm.
I saw 2 shows--Blue Man Group and Criss Angel's Believe. Loved them both. Blue Man Group was crazy cool. I was surprised by how funny they were, I mean, I thought they just banged on stuff, haha. Great show and affordable, especially compared to Cirque du Soleil's "O" which I would have loved to see. I would recommend Criss Angel if you are fans of him and his show Mindfreak.
Ok...this was hella long. My bad. Hope that helps spark some ideas.