It always takes me quite a while to dig my way through Intel's very messy website. To get to the free non-commercial software follow this link:
There are tons of useful things in there, such as ifort, icc, icpc and MKL (Intel's optimized LAPACK and BLAS implementations and more). You have to register, but pretty much everything is free as long as your work is non-commercial.
Another very useful page is the MKL Link Line Advisor:
Pretty much invaluable unless you know the flags by heart (sadly, I do!). Happy `ifort -O3`-ing!