Depends on what you want in the way of tools. If you're looking for tools to assist you with manual link building, I think the name brands currently are at places like seomoz, majestic,raven. I don't use any of them, I do see their names out there. I suspect those tools won't help you with the building, merely the identification and tracking.
If you want tools to actually build links, then you need to delve into tools that auto-post to blogs, forums, stuff like that. Tools like that are out there, unfortunately I don't know any specifics. Google or other forums that specialize more in churn and burn type tactics may be the place to research.