Zonajobs and Bumeran are the biggest online job boards but they will both ask for a cuit. If you publish on paper newspaper classifieds you won´t need a cuit. you also have smaller boards like computrabajo, buscojobs, trabajando, execuzone, universobit. You might also want to try LinkedIn social network. It also depends on what type of job you are willing to post...feel free to post here what it is about and I will try to help you out.