People use all kinds of stuff from Fruity Loops to Reason, Pro Tools to Cubase and everything inbetween.  Some even use combinations of these programs which is what I think is best.  There is no right answer.

For me, it is Reason 5 rewired into Pro Tools 9 for all your recording, sampling and beatmaking needs.  Reason has a multitude of sample libraries you can buy, download for free, or create your own.  Plus, with Reason 5's new internal sampling ability, there's not much you can't accomplish with it.

Also, there is much to be said for Pro Tools native instruments plugin.  That's a whole new ballgame all together.  

All this stuff, complete with a Yamaha Motif and maybe a Fantom rack thrown, and turntables makes for the ultimate beat setup….in my opinion of course.