Exactly what river said. Find an article directory list, then submit to them. Find a bunch of social bookmarking sites (shameless plug - mine is SoLinkable), then submit your articles to them. And finally, become active on forums such as these (with dofollow links). I think you'll find that pretty much everyone will have the exact same comment regarding this...
The thing is, there are powerful links and weak links. If you link from your signature here, does it pas any juice. Usually forum signature links are quite weak no? On the contrary, if you manage to get a link from a pr5 page, any pr5 page, this is worth so much more. The key is to get a few "potent" links, these are the ones which matter.
There are many ways to build quick links as said above but most of those are very weak links and do not do much for your PR. I think you still need to do these but do not rely on those solely at all to gain PR.
How about giving away freebies like a free website template or some web-based widget (tool) with your links embedded in them? Each time your freebie is downloaded and installed, you get a "free" one-way link, plus free publicity and possibly future traffic.