Lots of places offer this trip, though I booked mine through my holiday company. Basically, you get an early flight (about 8.15) to Cairo then spend around 12 hours being bussed about the city (an experience in itself) with a guide, flying back at about 9.15 in the evening so back to the hotel about 11.30.
The cost included: transfer from hotel to/from the airport, flights (with breakfast/snack), bus and admission to Muhammad Ali Mosque, the Pyramids (extra to go inside), the Sphinx, lunch at a 4/5* hotel, shopping opportunity at souvenir shop, Cairo museum (Tutankhamun gallery), Nile cruise with light evening meal/entertainment.
A whirlwind tour but a million times better than I'd expected (I was fulfilling a lifetime's dream anyway). There was time to get a taste of the main sites and just watching the people and the traffic as we drove round Cairo and Giza was fascinating, the guide was helpful and informative, I didn't spend any money at all (apart from buying water at the airport) and, all in all, it was an excellent if exhausting day.
It's not a cheap day out (around 200CY, which will be about 400 euros or so) but I thought it was good value for what I got. It certainly felt very well-organised and very safe (we had a security man on the coach, and a security car with lights and siren to speed us through the Cairo traffic).
I wouldn't recommend going in the summer; the temperatures in Egypt would make it a very unpleasant experience, I think, even though the coaches are air-conditioned. But in December, with the temperature in the high 60s, it was perfect. I'd also suggest taking the Friday tour, as Cairo is (slightly) less crowded and frantic on Fridays.

