I remember the three big ones as 3DS Max, Maya, and SoftImage. ...Is SoftImage still around any more? I haven't heard much of it...
Of the three (or two), I think 3DS Max is the friendliest. It will still take a great deal of time and effort to get to know it, but I think it's the most helpful in learning terms.
But those three are also all professional-level programs, and cost many monies. I know there are smaller-scale programs around (things like Blender), but I don't know too much of them. Blender does seem to be a free favorite, though.
Or if you just feel like playing around (and your computer can handle it) Sculptris is a neat program that tries a more intuitive approach to modeling. But last I heard, it wasn't so much an alternative to proper 3D modeling so much as a supplement, if you mean to make models for any kind of purpose (like games or animation)...
In any case, I think I'm a number of years out of touch, so that may not all be accurate.