LinkXL 
(that's the standard response out of the way)
PRweb's alright; get some
iSnare credits while you're at it. You can't go wrong with some
automated submissions, either.
dmoz submissions are always great to get in, given how many people simply mirror the directory. Submit (expect nothing, but submit anyway!). There are editors hanging around in EFnet #seo who might be able to help you out.
Put up an RSS feed of your latest content, and get this submitted everywhere, twice if neccessary.
You can always slap up some linkbait for bursty traffic from social media; similarly, if you're a business site, spending a bit of time crafting a good handwritten article and getting it published by a business news site may snag you a good link.
Past that, you can start looking at where your competitors get theirs, and copying them - one simple way of tackling these is to do it once or twice, build a step-by-step guide detailing exactly what constitutes a "good link" and how to get one, and outsource the process.