Wow. A lot of Rand hate from people who haven't read her books enough to actually form an opinion. As a liberal, I say read Atlas Shrugged, keep an open mind, and wait to make a judgement until the end.
For me the most important thing she did was alter the rhetoric of philosophy. I come from an exceptionally liberal background, and with that comes a certain language when discussing topics. What you don't realize most of your youth is how much that language usage affects the way you understand issues. What Rand does is turn all of that rhetoric on its head. Instead of the selfless individual helping society, you have the leech living of of others' productivity. Instead of the greedy CEO, you have the brilliant producer who just wants an exchange of ideas.
I still reject most of her philosophy. I find her to be as naive as the far left in her understanding of human nature and her assertions as to what makes for a fulfilling existence. Furthermore, she herself at times falls into the trap of using her rhetoric to mask gaps in her arguments (although it's a novel--we can ease up on that a bit). What she did, though, was force me to reexamine my own beliefs and understand which ones I truly believed in, and which ones I believed in because of the language I understood them in. I believe I am a stronger, better informed person for having read her work, even though I disagree with much of the content.