Ditto - I had three weeks and needed more time!

BUt if you do the pyramids (which is a must), do it first thing in the morning. If you want to climb around inside the great and lesser pyramids, not only does it get hotter in the afternoons but they only sell 100 tickets per day. Once they sell out, tough luck. So if you want to get in, go early and buy your ticket. When i was there it was 100LE - roughly $20.

i would also recommend the Cairo Museum for the afternoon - oddly enough for the same reason. there is no air conditioning inside; so people tend to stay away in the afternoon. you'll have the place more to yourself and will be able to stand right next to the cases containing all the absolutely incredible artifacts whose detail you'll want to stare at for hours! i had two days alone in the museum and still didn't see everything! but the gold room and the mummies room are air conditioned if you need a break (100Le for the mummies room as well).

luxor museum is smaller but has high quality stuff. dont bother with the mummification museum in luxor.

if you're a marriott person (forgot to look before i replied), the marriott in zamalek is excellent. it's an old palace originally created for the opening of the suez canal to host princess eugenie. the main building of the hotel is still this palace (and it's gorgeous) with two towers on either side that compose the very modern rooms. it's right on the banks of the nile with nile views from every room. if there, get a massage - an hour for about 100LE. insane. actually get one from every hotel. your feet will hurt after all the walking every day anyway and they're so cheap!