Levers, rollers, ramps and lots of labor. I have to admit, all the furor over "HOW could the pyramids have been built?" seems pretty silly to me. When you keep in mind how long it takes and has taken people to build cathedrals - hundreds of years - it really makes the construction of a pile of large cut stones a lot less mysterious. It's not like the pyramids were built quickly; there's no reason to think that. Given enough time and labor, virtually any construction becomes possible.

Either the stones were cut and then moved into place, or they were rolled into place and then cut. In either case, they had to have used levers and ramps to get the stones into place.

I'm curious; how many different theories are there?

I always assumed it was just the fact that they had thousands and thousands of slaves---the sheer manpower made up for the lack of wheels.

What about the theory that they built them by simply adding sand and building up? If that makes sense.

Though it could be something to do with space wombats.

One of my profesors, made one of the theories of how the pyramids might have been built. She says that the pyramids weren't made with blocks of stone but they were chisel in a hill of calysa stone, the pyramid used to be a little hill.
If you think, to made the pyramid they would have need a thousands of trees that don't grew on egipt.
The theory may be a little different, but if you investigate and read what this profesor says you'll see that it very interesting and that make sense.
You can look for it by Amalia Frontini Theory

My most favored theory is that there was some kind of ramp that made the way to the unfinished layer and the stones were moved by a method of covering the 4 sides of the stone with some kind of large wheel and they also have developed simple machines that might have helped them.
Although some UFO enthusiasts said that they were helped by aliens and same theory applies to the Mesoamerican temples for their pyramidal shape.
Others, though prefer the Atlantis theory where Atlantians helped them, thus the same pyramidal structures appears in both Egypt and Mesoamerica.

Hebrew slaves (I don't care what Zahi Hawass says!).

Well, everything/everyone in Egypt belonged to Pharoh, right? So, everyone had to pitch in a little bit. It wasn't slaves that built it, but volunteers. They would cut stone from the mountains somewhere and take them down the Nile to the site of the pyramids being built. They would dig down into the ground and make the burial room, plus a room that was made to throw of thieves. Then they built over it and made ramps as it got taller. Then they smoothed it over and took the ramps down. Pretty simple really. Except the fact that it's simply not that simple.